Libraries: Move to Userland/Libraries/

Userland/Libraries/LibJS/Tests/builtins/Array/Array.from.js

@@ -0,0 +1,69 @@
+test("length is 1", () => {
+    expect(Array.from).toHaveLength(1);
+});
+
+describe("normal behavior", () => {
+    test("empty array", () => {
+        var a = Array.from([]);
+        expect(a instanceof Array).toBeTrue();
+        expect(a).toHaveLength(0);
+    });
+
+    test("empty string", () => {
+        var a = Array.from("");
+        expect(a instanceof Array).toBeTrue();
+        expect(a).toHaveLength(0);
+    });
+
+    test("non-empty array", () => {
+        var a = Array.from([5, 8, 1]);
+        expect(a instanceof Array).toBeTrue();
+        expect(a).toHaveLength(3);
+        expect(a[0]).toBe(5);
+        expect(a[1]).toBe(8);
+        expect(a[2]).toBe(1);
+    });
+
+    test("non-empty string", () => {
+        var a = Array.from("what");
+        expect(a instanceof Array).toBeTrue();
+        expect(a).toHaveLength(4);
+        expect(a[0]).toBe("w");
+        expect(a[1]).toBe("h");
+        expect(a[2]).toBe("a");
+        expect(a[3]).toBe("t");
+    });
+
+    test("shallow array copy", () => {
+        var a = [1, 2, 3];
+        var b = Array.from([a]);
+        expect(b instanceof Array).toBeTrue();
+        expect(b).toHaveLength(1);
+        b[0][0] = 4;
+        expect(a[0]).toBe(4);
+    });
+
+    test("from iterator", () => {
+        function rangeIterator(begin, end) {
+            return {
+                [Symbol.iterator]() {
+                    let value = begin - 1;
+                    return {
+                        next() {
+                            if (value < end) {
+                                value += 1;
+                            }
+                            return { value: value, done: value >= end };
+                        },
+                    };
+                },
+            };
+        }
+
+        var a = Array.from(rangeIterator(8, 10));
+        expect(a instanceof Array).toBeTrue();
+        expect(a).toHaveLength(2);
+        expect(a[0]).toBe(8);
+        expect(a[1]).toBe(9);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.isArray.js

@@ -0,0 +1,26 @@
+test("length is 1", () => {
+    expect(Array.isArray).toHaveLength(1);
+});
+
+test("arguments that evaluate to false", () => {
+    expect(Array.isArray()).toBeFalse();
+    expect(Array.isArray("1")).toBeFalse();
+    expect(Array.isArray("foo")).toBeFalse();
+    expect(Array.isArray(1)).toBeFalse();
+    expect(Array.isArray(1, 2, 3)).toBeFalse();
+    expect(Array.isArray(undefined)).toBeFalse();
+    expect(Array.isArray(null)).toBeFalse();
+    expect(Array.isArray(Infinity)).toBeFalse();
+    expect(Array.isArray({})).toBeFalse();
+});
+
+test("arguments that evaluate to true", () => {
+    expect(Array.isArray([])).toBeTrue();
+    expect(Array.isArray([1])).toBeTrue();
+    expect(Array.isArray([1, 2, 3])).toBeTrue();
+    expect(Array.isArray(new Array())).toBeTrue();
+    expect(Array.isArray(new Array(10))).toBeTrue();
+    expect(Array.isArray(new Array("a", "b", "c"))).toBeTrue();
+    // FIXME: Array.prototype is supposed to be an array!
+    // expect(Array.isArray(Array.prototype)).toBeTrue();
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.js

@@ -0,0 +1,53 @@
+test("constructor properties", () => {
+    expect(Array).toHaveLength(1);
+    expect(Array.name).toBe("Array");
+    expect(Array.prototype.length).toBe(0);
+});
+
+describe("errors", () => {
+    test("invalid array length", () => {
+        [-1, -100, -0.1, 0.1, 1.23, Infinity, -Infinity, NaN].forEach(value => {
+            expect(() => {
+                new Array(value);
+            }).toThrowWithMessage(RangeError, "Invalid array length");
+        });
+    });
+});
+
+describe("normal behavior", () => {
+    test("typeof", () => {
+        expect(typeof Array()).toBe("object");
+        expect(typeof new Array()).toBe("object");
+    });
+
+    test("constructor with single numeric argument", () => {
+        var a = new Array(5);
+        expect(a instanceof Array).toBeTrue();
+        expect(a).toHaveLength(5);
+    });
+
+    test("constructor with single non-numeric argument", () => {
+        var a = new Array("5");
+        expect(a instanceof Array).toBeTrue();
+        expect(a).toHaveLength(1);
+        expect(a[0]).toBe("5");
+    });
+
+    test("constructor with multiple numeric arguments", () => {
+        var a = new Array(1, 2, 3);
+        expect(a instanceof Array).toBeTrue();
+        expect(a).toHaveLength(3);
+        expect(a[0]).toBe(1);
+        expect(a[1]).toBe(2);
+        expect(a[2]).toBe(3);
+    });
+
+    test("constructor with single array argument", () => {
+        var a = new Array([1, 2, 3]);
+        expect(a instanceof Array).toBeTrue();
+        expect(a).toHaveLength(1);
+        expect(a[0][0]).toBe(1);
+        expect(a[0][1]).toBe(2);
+        expect(a[0][2]).toBe(3);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.of.js

@@ -0,0 +1,59 @@
+test("length is 0", () => {
+    expect(Array.of).toHaveLength(0);
+});
+
+describe("normal behavior", () => {
+    test("single numeric argument", () => {
+        var a = Array.of(5);
+        expect(a instanceof Array).toBeTrue();
+        expect(a).toHaveLength(1);
+        expect(a[0]).toBe(5);
+    });
+
+    test("single non-numeric argument", () => {
+        var a = Array.of("5");
+        expect(a instanceof Array).toBeTrue();
+        expect(a).toHaveLength(1);
+        expect(a[0]).toBe("5");
+    });
+
+    test("single infinite numeric argument", () => {
+        var a = Array.of(Infinity);
+        expect(a instanceof Array).toBeTrue();
+        expect(a).toHaveLength(1);
+        expect(a[0]).toBe(Infinity);
+    });
+
+    test("multiple numeric arguments", () => {
+        var a = Array.of(1, 2, 3);
+        expect(a instanceof Array).toBeTrue();
+        expect(a).toHaveLength(3);
+        expect(a[0]).toBe(1);
+        expect(a[1]).toBe(2);
+        expect(a[2]).toBe(3);
+    });
+
+    test("single array argument", () => {
+        var a = Array.of([1, 2, 3]);
+        expect(a instanceof Array).toBeTrue();
+        expect(a).toHaveLength(1);
+        expect(a[0][0]).toBe(1);
+        expect(a[0][1]).toBe(2);
+        expect(a[0][2]).toBe(3);
+    });
+
+    test("getter property is included in returned array", () => {
+        var t = [1, 2, 3];
+        Object.defineProperty(t, 3, {
+            get() {
+                return 4;
+            },
+        });
+        var a = Array.of(...t);
+        expect(a).toHaveLength(4);
+        expect(a[0]).toBe(1);
+        expect(a[1]).toBe(2);
+        expect(a[2]).toBe(3);
+        expect(a[3]).toBe(4);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype-generic-functions.js

@@ -0,0 +1,150 @@
+describe("ability to work with generic non-array objects", () => {
+    test("push, pop", () => {
+        [undefined, "foo", -42, 0].forEach(length => {
+            const o = { length };
+
+            expect(Array.prototype.push.call(o, "foo")).toBe(1);
+            expect(o).toHaveLength(1);
+            expect(o[0]).toBe("foo");
+            expect(Array.prototype.push.call(o, "bar", "baz")).toBe(3);
+            expect(o).toHaveLength(3);
+            expect(o[0]).toBe("foo");
+            expect(o[1]).toBe("bar");
+            expect(o[2]).toBe("baz");
+
+            expect(Array.prototype.pop.call(o)).toBe("baz");
+            expect(o).toHaveLength(2);
+            expect(Array.prototype.pop.call(o)).toBe("bar");
+            expect(o).toHaveLength(1);
+            expect(Array.prototype.pop.call(o)).toBe("foo");
+            expect(o).toHaveLength(0);
+            expect(Array.prototype.pop.call(o)).toBeUndefined();
+            expect(o).toHaveLength(0);
+
+            o.length = length;
+            expect(Array.prototype.pop.call(o)).toBeUndefined();
+            expect(o).toHaveLength(0);
+        });
+    });
+
+    test("splice", () => {
+        const o = { length: 3, 0: "hello", 2: "serenity" };
+        const removed = Array.prototype.splice.call(o, 0, 2, "hello", "friends");
+        expect(o).toHaveLength(3);
+        expect(o[0]).toBe("hello");
+        expect(o[1]).toBe("friends");
+        expect(o[2]).toBe("serenity");
+        expect(removed).toHaveLength(2);
+        expect(removed[0]).toBe("hello");
+        expect(removed[1]).toBeUndefined();
+    });
+
+    test("join", () => {
+        expect(Array.prototype.join.call({})).toBe("");
+        expect(Array.prototype.join.call({ length: "foo" })).toBe("");
+        expect(Array.prototype.join.call({ length: 3 })).toBe(",,");
+        expect(Array.prototype.join.call({ length: 2, 0: "foo", 1: "bar" })).toBe("foo,bar");
+        expect(Array.prototype.join.call({ length: 2, 0: "foo", 1: "bar", 2: "baz" })).toBe(
+            "foo,bar"
+        );
+        expect(Array.prototype.join.call({ length: 3, 1: "bar" }, "~")).toBe("~bar~");
+        expect(Array.prototype.join.call({ length: 3, 0: "foo", 1: "bar", 2: "baz" }, "~")).toBe(
+            "foo~bar~baz"
+        );
+    });
+
+    // FIXME: test-js asserts when this is just called "toString" ಠ_ಠ
+    test("toString (FIXME)", () => {
+        expect(Array.prototype.toString.call({})).toBe("[object Object]");
+        expect(Array.prototype.toString.call({ join: "foo" })).toBe("[object Object]");
+        expect(Array.prototype.toString.call({ join: () => "foo" })).toBe("foo");
+    });
+
+    test("indexOf", () => {
+        expect(Array.prototype.indexOf.call({})).toBe(-1);
+        expect(Array.prototype.indexOf.call({ 0: undefined })).toBe(-1);
+        expect(Array.prototype.indexOf.call({ length: 1, 0: undefined })).toBe(0);
+        expect(Array.prototype.indexOf.call({ length: 1, 2: "foo" }, "foo")).toBe(-1);
+        expect(Array.prototype.indexOf.call({ length: 5, 2: "foo" }, "foo")).toBe(2);
+        expect(Array.prototype.indexOf.call({ length: 5, 2: "foo", 4: "foo" }, "foo", 3)).toBe(4);
+    });
+
+    test("lastIndexOf", () => {
+        expect(Array.prototype.lastIndexOf.call({})).toBe(-1);
+        expect(Array.prototype.lastIndexOf.call({ 0: undefined })).toBe(-1);
+        expect(Array.prototype.lastIndexOf.call({ length: 1, 0: undefined })).toBe(0);
+        expect(Array.prototype.lastIndexOf.call({ length: 1, 2: "foo" }, "foo")).toBe(-1);
+        expect(Array.prototype.lastIndexOf.call({ length: 5, 2: "foo" }, "foo")).toBe(2);
+        expect(Array.prototype.lastIndexOf.call({ length: 5, 2: "foo", 4: "foo" }, "foo")).toBe(4);
+        expect(Array.prototype.lastIndexOf.call({ length: 5, 2: "foo", 4: "foo" }, "foo", -2)).toBe(
+            2
+        );
+    });
+
+    test("includes", () => {
+        expect(Array.prototype.includes.call({})).toBeFalse();
+        expect(Array.prototype.includes.call({ 0: undefined })).toBeFalse();
+        expect(Array.prototype.includes.call({ length: 1, 0: undefined })).toBeTrue();
+        expect(Array.prototype.includes.call({ length: 1, 2: "foo" }, "foo")).toBeFalse();
+        expect(Array.prototype.includes.call({ length: 5, 2: "foo" }, "foo")).toBeTrue();
+    });
+
+    const o = { length: 5, 0: "foo", 1: "bar", 3: "baz" };
+
+    test("every", () => {
+        const visited = [];
+        Array.prototype.every.call(o, value => {
+            visited.push(value);
+            return true;
+        });
+        expect(visited).toEqual(["foo", "bar", "baz"]);
+    });
+
+    test("find, findIndex", () => {
+        ["find", "findIndex"].forEach(name => {
+            const visited = [];
+            Array.prototype[name].call(o, value => {
+                visited.push(value);
+                return false;
+            });
+            expect(visited).toEqual(["foo", "bar", undefined, "baz", undefined]);
+        });
+    });
+
+    test("filter, forEach, map, some", () => {
+        ["filter", "forEach", "map", "some"].forEach(name => {
+            const visited = [];
+            Array.prototype[name].call(o, value => {
+                visited.push(value);
+                return false;
+            });
+            expect(visited).toEqual(["foo", "bar", "baz"]);
+        });
+    });
+
+    test("reduce", () => {
+        const visited = [];
+        Array.prototype.reduce.call(
+            o,
+            (_, value) => {
+                visited.push(value);
+                return false;
+            },
+            "initial"
+        );
+        expect(visited).toEqual(["foo", "bar", "baz"]);
+    });
+
+    test("reduceRight", () => {
+        const visited = [];
+        Array.prototype.reduceRight.call(
+            o,
+            (_, value) => {
+                visited.push(value);
+                return false;
+            },
+            "initial"
+        );
+        expect(visited).toEqual(["baz", "bar", "foo"]);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.concat.js

@@ -0,0 +1,43 @@
+test("length is 1", () => {
+    expect(Array.prototype.concat).toHaveLength(1);
+});
+
+describe("normal behavior", () => {
+    var array = ["hello"];
+
+    test("no arguments", () => {
+        var concatenated = array.concat();
+        expect(array).toHaveLength(1);
+        expect(concatenated).toHaveLength(1);
+    });
+
+    test("single argument", () => {
+        var concatenated = array.concat("friends");
+        expect(array).toHaveLength(1);
+        expect(concatenated).toHaveLength(2);
+        expect(concatenated[0]).toBe("hello");
+        expect(concatenated[1]).toBe("friends");
+    });
+
+    test("single array argument", () => {
+        var concatenated = array.concat([1, 2, 3]);
+        expect(array).toHaveLength(1);
+        expect(concatenated).toHaveLength(4);
+        expect(concatenated[0]).toBe("hello");
+        expect(concatenated[1]).toBe(1);
+        expect(concatenated[2]).toBe(2);
+        expect(concatenated[3]).toBe(3);
+    });
+
+    test("multiple arguments", () => {
+        var concatenated = array.concat(false, "serenity", { name: "libjs" }, [1, [2, 3]]);
+        expect(array).toHaveLength(1);
+        expect(concatenated).toHaveLength(6);
+        expect(concatenated[0]).toBe("hello");
+        expect(concatenated[1]).toBeFalse();
+        expect(concatenated[2]).toBe("serenity");
+        expect(concatenated[3]).toEqual({ name: "libjs" });
+        expect(concatenated[4]).toBe(1);
+        expect(concatenated[5]).toEqual([2, 3]);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.every.js

@@ -0,0 +1,55 @@
+test("length is 1", () => {
+    expect(Array.prototype.every).toHaveLength(1);
+});
+
+describe("errors", () => {
+    test("requires at least one argument", () => {
+        expect(() => {
+            [].every();
+        }).toThrowWithMessage(TypeError, "Array.prototype.every() requires at least one argument");
+    });
+
+    test("callback must be a function", () => {
+        expect(() => {
+            [].every(undefined);
+        }).toThrowWithMessage(TypeError, "undefined is not a function");
+    });
+});
+
+describe("normal behavior", () => {
+    test("basic functionality", () => {
+        var arrayOne = ["serenity", { test: "serenity" }];
+        var arrayTwo = [true, false, 1, 2, 3, "3"];
+
+        expect(arrayOne.every(value => value === "hello")).toBeFalse();
+        expect(arrayOne.every(value => value === "serenity")).toBeFalse();
+        expect(arrayOne.every((value, index, arr) => index < 2)).toBeTrue();
+        expect(arrayOne.every(value => typeof value === "string")).toBeFalse();
+        expect(arrayOne.every(value => arrayOne.pop())).toBeTrue();
+
+        expect(arrayTwo.every((value, index, arr) => index > 0)).toBeFalse();
+        expect(arrayTwo.every((value, index, arr) => index >= 0)).toBeTrue();
+        expect(arrayTwo.every(value => typeof value !== "string")).toBeFalse();
+        expect(arrayTwo.every(value => typeof value === "number")).toBeFalse();
+        expect(arrayTwo.every(value => value > 0)).toBeFalse();
+        expect(arrayTwo.every(value => value >= 0 && value < 4)).toBeTrue();
+        expect(arrayTwo.every(value => arrayTwo.pop())).toBeTrue();
+
+        expect(["", "hello", "friends", "serenity"].every(value => value.length >= 0)).toBeTrue();
+    });
+
+    test("empty array", () => {
+        expect([].every(value => value === 1)).toBeTrue();
+    });
+
+    test("elements past the initial array size are ignored", () => {
+        var array = [1, 2, 3, 4, 5];
+
+        expect(
+            arrayTwo.every((value, index, arr) => {
+                arr.push(6);
+                return value <= 5;
+            })
+        ).toBeTrue();
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.fill.js

@@ -0,0 +1,20 @@
+test("length is 1", () => {
+    expect(Array.prototype.fill).toHaveLength(1);
+});
+
+test("basic functionality", () => {
+    var array = [1, 2, 3, 4];
+
+    expect(array.fill(0, 2, 4)).toEqual([1, 2, 0, 0]);
+    expect(array.fill(5, 1)).toEqual([1, 5, 5, 5]);
+    expect(array.fill(6)).toEqual([6, 6, 6, 6]);
+
+    expect([1, 2, 3].fill(4)).toEqual([4, 4, 4]);
+    expect([1, 2, 3].fill(4, 1)).toEqual([1, 4, 4]);
+    expect([1, 2, 3].fill(4, 1, 2)).toEqual([1, 4, 3]);
+    expect([1, 2, 3].fill(4, 3, 3)).toEqual([1, 2, 3]);
+    expect([1, 2, 3].fill(4, -3, -2)).toEqual([4, 2, 3]);
+    expect([1, 2, 3].fill(4, NaN, NaN)).toEqual([1, 2, 3]);
+    expect([1, 2, 3].fill(4, 3, 5)).toEqual([1, 2, 3]);
+    expect(Array(3).fill(4)).toEqual([4, 4, 4]);
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.filter.js

@@ -0,0 +1,68 @@
+test("length is 1", () => {
+    expect(Array.prototype.filter).toHaveLength(1);
+});
+
+describe("errors", () => {
+    test("requires at least one argument", () => {
+        expect(() => {
+            [].filter();
+        }).toThrowWithMessage(TypeError, "Array.prototype.filter() requires at least one argument");
+    });
+
+    test("callback must be a function", () => {
+        expect(() => {
+            [].filter(undefined);
+        }).toThrowWithMessage(TypeError, "undefined is not a function");
+    });
+});
+
+describe("normal behavior", () => {
+    test("never calls callback with empty array", () => {
+        var callbackCalled = 0;
+        expect(
+            [].filter(() => {
+                callbackCalled++;
+            })
+        ).toEqual([]);
+        expect(callbackCalled).toBe(0);
+    });
+
+    test("calls callback once for every item", () => {
+        var callbackCalled = 0;
+        expect(
+            [1, 2, 3].filter(() => {
+                callbackCalled++;
+            })
+        ).toEqual([]);
+        expect(callbackCalled).toBe(3);
+    });
+
+    test("can filter based on callback return value", () => {
+        var evenNumbers = [0, 1, 2, 3, 4, 5, 6, 7].filter(x => x % 2 === 0);
+        expect(evenNumbers).toEqual([0, 2, 4, 6]);
+
+        var fruits = [
+            "Apple",
+            "Banana",
+            "Blueberry",
+            "Grape",
+            "Mango",
+            "Orange",
+            "Peach",
+            "Pineapple",
+            "Raspberry",
+            "Watermelon",
+        ];
+        const filterItems = (arr, query) => {
+            return arr.filter(el => el.toLowerCase().indexOf(query.toLowerCase()) !== -1);
+        };
+        expect(filterItems(fruits, "Berry")).toEqual(["Blueberry", "Raspberry"]);
+        expect(filterItems(fruits, "P")).toEqual([
+            "Apple",
+            "Grape",
+            "Peach",
+            "Pineapple",
+            "Raspberry",
+        ]);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.find.js

@@ -0,0 +1,65 @@
+test("length is 1", () => {
+    expect(Array.prototype.find).toHaveLength(1);
+});
+
+describe("errors", () => {
+    test("requires at least one argument", () => {
+        expect(() => {
+            [].find();
+        }).toThrowWithMessage(TypeError, "Array.prototype.find() requires at least one argument");
+    });
+
+    test("callback must be a function", () => {
+        expect(() => {
+            [].find(undefined);
+        }).toThrowWithMessage(TypeError, "undefined is not a function");
+    });
+});
+
+describe("normal behavior", () => {
+    test("basic functionality", () => {
+        var array = ["hello", "friends", 1, 2, false];
+
+        expect(array.find(value => value === "hello")).toBe("hello");
+        expect(array.find((value, index, arr) => index === 1)).toBe("friends");
+        expect(array.find(value => value == "1")).toBe(1);
+        expect(array.find(value => value === 1)).toBe(1);
+        expect(array.find(value => typeof value !== "string")).toBe(1);
+        expect(array.find(value => typeof value === "boolean")).toBeFalse();
+        expect(array.find(value => value > 1)).toBe(2);
+        expect(array.find(value => value > 1 && value < 3)).toBe(2);
+        expect(array.find(value => value > 100)).toBeUndefined();
+        expect([].find(value => value === 1)).toBeUndefined();
+    });
+
+    test("never calls callback with empty array", () => {
+        var callbackCalled = 0;
+        expect(
+            [].find(() => {
+                callbackCalled++;
+            })
+        ).toBeUndefined();
+        expect(callbackCalled).toBe(0);
+    });
+
+    test("calls callback once for every item", () => {
+        var callbackCalled = 0;
+        expect(
+            [1, 2, 3].find(() => {
+                callbackCalled++;
+            })
+        ).toBeUndefined();
+        expect(callbackCalled).toBe(3);
+    });
+
+    test("empty slots are treated as undefined", () => {
+        var callbackCalled = 0;
+        expect(
+            [1, , , "foo", , undefined, , ,].find(value => {
+                callbackCalled++;
+                return value === undefined;
+            })
+        ).toBeUndefined();
+        expect(callbackCalled).toBe(2);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.findIndex.js

@@ -0,0 +1,68 @@
+test("length is 1", () => {
+    expect(Array.prototype.findIndex).toHaveLength(1);
+});
+
+describe("errors", () => {
+    test("requires at least one argument", () => {
+        expect(() => {
+            [].findIndex();
+        }).toThrowWithMessage(
+            TypeError,
+            "Array.prototype.findIndex() requires at least one argument"
+        );
+    });
+
+    test("callback must be a function", () => {
+        expect(() => {
+            [].findIndex(undefined);
+        }).toThrowWithMessage(TypeError, "undefined is not a function");
+    });
+});
+
+describe("normal behavior", () => {
+    test("basic functionality", () => {
+        var array = ["hello", "friends", 1, 2, false];
+
+        expect(array.findIndex(value => value === "hello")).toBe(0);
+        expect(array.findIndex((value, index, arr) => index === 1)).toBe(1);
+        expect(array.findIndex(value => value == "1")).toBe(2);
+        expect(array.findIndex(value => value === 1)).toBe(2);
+        expect(array.findIndex(value => typeof value !== "string")).toBe(2);
+        expect(array.findIndex(value => typeof value === "boolean")).toBe(4);
+        expect(array.findIndex(value => value > 1)).toBe(3);
+        expect(array.findIndex(value => value > 1 && value < 3)).toBe(3);
+        expect(array.findIndex(value => value > 100)).toBe(-1);
+        expect([].findIndex(value => value === 1)).toBe(-1);
+    });
+
+    test("never calls callback with empty array", () => {
+        var callbackCalled = 0;
+        expect(
+            [].findIndex(() => {
+                callbackCalled++;
+            })
+        ).toBe(-1);
+        expect(callbackCalled).toBe(0);
+    });
+
+    test("calls callback once for every item", () => {
+        var callbackCalled = 0;
+        expect(
+            [1, 2, 3].findIndex(() => {
+                callbackCalled++;
+            })
+        ).toBe(-1);
+        expect(callbackCalled).toBe(3);
+    });
+
+    test("empty slots are treated as undefined", () => {
+        var callbackCalled = 0;
+        expect(
+            [1, , , "foo", , undefined, , ,].findIndex(value => {
+                callbackCalled++;
+                return value === undefined;
+            })
+        ).toBe(1);
+        expect(callbackCalled).toBe(2);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.forEach.js

@@ -0,0 +1,70 @@
+test("length is 1", () => {
+    expect(Array.prototype.forEach).toHaveLength(1);
+});
+
+describe("errors", () => {
+    test("requires at least one argument", () => {
+        expect(() => {
+            [].forEach();
+        }).toThrowWithMessage(
+            TypeError,
+            "Array.prototype.forEach() requires at least one argument"
+        );
+    });
+
+    test("callback must be a function", () => {
+        expect(() => {
+            [].forEach(undefined);
+        }).toThrowWithMessage(TypeError, "undefined is not a function");
+    });
+});
+
+describe("normal behavior", () => {
+    test("never calls callback with empty array", () => {
+        var callbackCalled = 0;
+        expect(
+            [].forEach(() => {
+                callbackCalled++;
+            })
+        ).toBeUndefined();
+        expect(callbackCalled).toBe(0);
+    });
+
+    test("calls callback once for every item", () => {
+        var callbackCalled = 0;
+        expect(
+            [1, 2, 3].forEach(() => {
+                callbackCalled++;
+            })
+        ).toBeUndefined();
+        expect(callbackCalled).toBe(3);
+    });
+
+    test("callback receives value and index", () => {
+        var a = [1, 2, 3];
+        a.forEach((value, index) => {
+            expect(value).toBe(a[index]);
+            expect(index).toBe(a[index] - 1);
+        });
+    });
+
+    test("callback receives array", () => {
+        var callbackCalled = 0;
+        var a = [1, 2, 3];
+        a.forEach((_, __, array) => {
+            callbackCalled++;
+            expect(a).toEqual(array);
+            a.push("test");
+        });
+        expect(callbackCalled).toBe(3);
+        expect(a).toEqual([1, 2, 3, "test", "test", "test"]);
+    });
+
+    test("this value can be modified", () => {
+        var t = [];
+        [1, 2, 3].forEach(function (value) {
+            this.push(value);
+        }, t);
+        expect(t).toEqual([1, 2, 3]);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.includes.js

@@ -0,0 +1,18 @@
+test("length is 1", () => {
+    expect(Array.prototype.includes).toHaveLength(1);
+});
+
+test("basic functionality", () => {
+    var array = ["hello", "friends", 1, 2, false];
+
+    expect([].includes()).toBeFalse();
+    expect([undefined].includes()).toBeTrue();
+    expect(array.includes("hello")).toBeTrue();
+    expect(array.includes(1)).toBeTrue();
+    expect(array.includes(1, -3)).toBeTrue();
+    expect(array.includes("serenity")).toBeFalse();
+    expect(array.includes(false, -1)).toBeTrue();
+    expect(array.includes(2, -1)).toBeFalse();
+    expect(array.includes(2, -100)).toBeTrue();
+    expect(array.includes("friends", 100)).toBeFalse();
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.indexOf.js

@@ -0,0 +1,25 @@
+test("length is 1", () => {
+    expect(Array.prototype.indexOf).toHaveLength(1);
+});
+
+test("basic functionality", () => {
+    var array = ["hello", "friends", 1, 2, false];
+
+    expect(array.indexOf("hello")).toBe(0);
+    expect(array.indexOf("friends")).toBe(1);
+    expect(array.indexOf(false)).toBe(4);
+    expect(array.indexOf(false, 2)).toBe(4);
+    expect(array.indexOf(false, -2)).toBe(4);
+    expect(array.indexOf(1)).toBe(2);
+    expect(array.indexOf(1, 1000)).toBe(-1);
+    expect(array.indexOf(1, -1000)).toBe(2);
+    expect(array.indexOf("serenity")).toBe(-1);
+    expect(array.indexOf(false, -1)).toBe(4);
+    expect(array.indexOf(2, -1)).toBe(-1);
+    expect(array.indexOf(2, -2)).toBe(3);
+    expect([].indexOf("serenity")).toBe(-1);
+    expect([].indexOf("serenity", 10)).toBe(-1);
+    expect([].indexOf("serenity", -10)).toBe(-1);
+    expect([].indexOf()).toBe(-1);
+    expect([undefined].indexOf()).toBe(0);
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.join.js

@@ -0,0 +1,24 @@
+test("length is 1", () => {
+    expect(Array.prototype.join).toHaveLength(1);
+});
+
+test("basic functionality", () => {
+    expect(["hello", "friends"].join()).toBe("hello,friends");
+    expect(["hello", "friends"].join(undefined)).toBe("hello,friends");
+    expect(["hello", "friends"].join(" ")).toBe("hello friends");
+    expect(["hello", "friends", "foo"].join("~", "#")).toBe("hello~friends~foo");
+    expect([].join()).toBe("");
+    expect([null].join()).toBe("");
+    expect([undefined].join()).toBe("");
+    expect([undefined, null, ""].join()).toBe(",,");
+    expect([1, null, 2, undefined, 3].join()).toBe("1,,2,,3");
+    expect(Array(3).join()).toBe(",,");
+});
+
+test("circular references", () => {
+    const a = ["foo", [], [1, 2, []], ["bar"]];
+    a[1] = a;
+    a[2][2] = a;
+    // [ "foo", <circular>, [ 1, 2, <circular> ], [ "bar" ] ]
+    expect(a.join()).toBe("foo,,1,2,,bar");
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.lastIndexOf.js

@@ -0,0 +1,22 @@
+test("length is 1", () => {
+    expect(Array.prototype.lastIndexOf).toHaveLength(1);
+});
+
+test("basic functionality", () => {
+    var array = [1, 2, 3, 1, "hello"];
+
+    expect(array.lastIndexOf("hello")).toBe(4);
+    expect(array.lastIndexOf("hello", 1000)).toBe(4);
+    expect(array.lastIndexOf(1)).toBe(3);
+    expect(array.lastIndexOf(1, -1)).toBe(3);
+    expect(array.lastIndexOf(1, -2)).toBe(3);
+    expect(array.lastIndexOf(2)).toBe(1);
+    expect(array.lastIndexOf(2, -3)).toBe(1);
+    expect(array.lastIndexOf(2, -4)).toBe(1);
+    expect([].lastIndexOf("hello")).toBe(-1);
+    expect([].lastIndexOf("hello", 10)).toBe(-1);
+    expect([].lastIndexOf("hello", -10)).toBe(-1);
+    expect([].lastIndexOf()).toBe(-1);
+    expect([undefined].lastIndexOf()).toBe(0);
+    expect([undefined, undefined, undefined].lastIndexOf()).toBe(2);
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.map.js

@@ -0,0 +1,57 @@
+test("length is 1", () => {
+    expect(Array.prototype.map).toHaveLength(1);
+});
+
+describe("errors", () => {
+    test("requires at least one argument", () => {
+        expect(() => {
+            [].map();
+        }).toThrowWithMessage(TypeError, "Array.prototype.map() requires at least one argument");
+    });
+
+    test("callback must be a function", () => {
+        expect(() => {
+            [].map(undefined);
+        }).toThrowWithMessage(TypeError, "undefined is not a function");
+    });
+});
+
+describe("normal behavior", () => {
+    test("never calls callback with empty array", () => {
+        var callbackCalled = 0;
+        expect(
+            [].map(() => {
+                callbackCalled++;
+            })
+        ).toEqual([]);
+        expect(callbackCalled).toBe(0);
+    });
+
+    test("calls callback once for every item", () => {
+        var callbackCalled = 0;
+        expect(
+            [1, 2, 3].map(() => {
+                callbackCalled++;
+            })
+        ).toEqual([undefined, undefined, undefined]);
+        expect(callbackCalled).toBe(3);
+    });
+
+    test("can map based on callback return value", () => {
+        expect(
+            [undefined, null, true, "foo", 42, {}].map(
+                (value, index) => "" + index + " -> " + value
+            )
+        ).toEqual([
+            "0 -> undefined",
+            "1 -> null",
+            "2 -> true",
+            "3 -> foo",
+            "4 -> 42",
+            "5 -> [object Object]",
+        ]);
+
+        var squaredNumbers = [0, 1, 2, 3, 4].map(x => x ** 2);
+        expect(squaredNumbers).toEqual([0, 1, 4, 9, 16]);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.pop.js

@@ -0,0 +1,29 @@
+test("length is 0", () => {
+    expect(Array.prototype.pop).toHaveLength(0);
+});
+
+describe("normal behavior", () => {
+    test("array with elements", () => {
+        var a = [1, 2, 3];
+        expect(a.pop()).toBe(3);
+        expect(a).toEqual([1, 2]);
+        expect(a.pop()).toBe(2);
+        expect(a).toEqual([1]);
+        expect(a.pop()).toBe(1);
+        expect(a).toEqual([]);
+        expect(a.pop()).toBeUndefined();
+        expect(a).toEqual([]);
+    });
+
+    test("empty array", () => {
+        var a = [];
+        expect(a.pop()).toBeUndefined();
+        expect(a).toEqual([]);
+    });
+
+    test("array with empty slot", () => {
+        var a = [,];
+        expect(a.pop()).toBeUndefined();
+        expect(a).toEqual([]);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.push.js

@@ -0,0 +1,23 @@
+test("length is 1", () => {
+    expect(Array.prototype.push).toHaveLength(1);
+});
+
+describe("normal behavior", () => {
+    test("no argument", () => {
+        var a = ["hello"];
+        expect(a.push()).toBe(1);
+        expect(a).toEqual(["hello"]);
+    });
+
+    test("single argument", () => {
+        var a = ["hello"];
+        expect(a.push("friends")).toBe(2);
+        expect(a).toEqual(["hello", "friends"]);
+    });
+
+    test("multiple arguments", () => {
+        var a = ["hello", "friends"];
+        expect(a.push(1, 2, 3)).toBe(5);
+        expect(a).toEqual(["hello", "friends", 1, 2, 3]);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.reduce.js

@@ -0,0 +1,113 @@
+test("length is 1", () => {
+    expect(Array.prototype.reduce).toHaveLength(1);
+});
+
+describe("errors", () => {
+    test("requires at least one argument", () => {
+        expect(() => {
+            [].reduce();
+        }).toThrowWithMessage(TypeError, "Array.prototype.reduce() requires at least one argument");
+    });
+
+    test("callback must be a function", () => {
+        expect(() => {
+            [].reduce(undefined);
+        }).toThrowWithMessage(TypeError, "undefined is not a function");
+    });
+
+    test("reduce of empty array with no initial value", () => {
+        expect(() => {
+            [].reduce((a, x) => x);
+        }).toThrowWithMessage(TypeError, "Reduce of empty array with no initial value");
+    });
+
+    test("reduce of array with only empty slots and no initial value", () => {
+        expect(() => {
+            [, ,].reduce((a, x) => x);
+        }).toThrowWithMessage(TypeError, "Reduce of empty array with no initial value");
+    });
+});
+
+describe("normal behavior", () => {
+    test("basic functionality", () => {
+        [1, 2].reduce(function () {
+            expect(this).toBeUndefined();
+        });
+
+        var callbackCalled = 0;
+        var callback = () => {
+            callbackCalled++;
+            return true;
+        };
+
+        expect([1].reduce(callback)).toBe(1);
+        expect(callbackCalled).toBe(0);
+
+        expect([, 1].reduce(callback)).toBe(1);
+        expect(callbackCalled).toBe(0);
+
+        callbackCalled = 0;
+        expect([1, 2, 3].reduce(callback)).toBeTrue();
+        expect(callbackCalled).toBe(2);
+
+        callbackCalled = 0;
+        expect([, , 1, 2, 3].reduce(callback)).toBeTrue();
+        expect(callbackCalled).toBe(2);
+
+        callbackCalled = 0;
+        expect([1, , , 10, , 100, , ,].reduce(callback)).toBeTrue();
+        expect(callbackCalled).toBe(2);
+
+        var constantlySad = () => ":^(";
+        var result = [].reduce(constantlySad, ":^)");
+        expect(result).toBe(":^)");
+
+        result = [":^0"].reduce(constantlySad, ":^)");
+        expect(result).toBe(":^(");
+
+        result = [":^0"].reduce(constantlySad);
+        expect(result).toBe(":^0");
+
+        result = [5, 4, 3, 2, 1].reduce((accum, elem) => accum + elem);
+        expect(result).toBe(15);
+
+        result = [1, 2, 3, 4, 5, 6].reduce((accum, elem) => accum + elem, 100);
+        expect(result).toBe(121);
+
+        result = [6, 5, 4, 3, 2, 1].reduce((accum, elem) => {
+            return accum + elem;
+        }, 100);
+        expect(result).toBe(121);
+
+        var indexes = [];
+        result = ["foo", 1, true].reduce((a, v, i) => {
+            indexes.push(i);
+        });
+        expect(result).toBeUndefined();
+        expect(indexes.length).toBe(2);
+        expect(indexes[0]).toBe(1);
+        expect(indexes[1]).toBe(2);
+
+        indexes = [];
+        result = ["foo", 1, true].reduce((a, v, i) => {
+            indexes.push(i);
+        }, "foo");
+        expect(result).toBeUndefined();
+        expect(indexes).toEqual([0, 1, 2]);
+
+        var mutable = { prop: 0 };
+        result = ["foo", 1, true].reduce((a, v) => {
+            a.prop = v;
+            return a;
+        }, mutable);
+        expect(result).toBe(mutable);
+        expect(result.prop).toBeTrue();
+
+        var a1 = [1, 2];
+        var a2 = null;
+        a1.reduce((a, v, i, t) => {
+            a2 = t;
+        });
+        expect(a1).toBe(a2);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.reduceRight.js

@@ -0,0 +1,118 @@
+test("length is 1", () => {
+    expect(Array.prototype.reduceRight).toHaveLength(1);
+});
+
+describe("errors", () => {
+    test("requires at least one argument", () => {
+        expect(() => {
+            [].reduceRight();
+        }).toThrowWithMessage(
+            TypeError,
+            "Array.prototype.reduceRight() requires at least one argument"
+        );
+    });
+
+    test("callback must be a function", () => {
+        expect(() => {
+            [].reduceRight(undefined);
+        }).toThrowWithMessage(TypeError, "undefined is not a function");
+    });
+
+    test("reduce of empty array with no initial value", () => {
+        expect(() => {
+            [].reduceRight((a, x) => x);
+        }).toThrowWithMessage(TypeError, "Reduce of empty array with no initial value");
+    });
+
+    test("reduce of array with only empty slots and no initial value", () => {
+        expect(() => {
+            [, ,].reduceRight((a, x) => x);
+        }).toThrowWithMessage(TypeError, "Reduce of empty array with no initial value");
+    });
+});
+
+describe("normal behavior", () => {
+    test("basic functionality", () => {
+        [1, 2].reduceRight(function () {
+            expect(this).toBeUndefined();
+        });
+
+        var callbackCalled = 0;
+        var callback = () => {
+            callbackCalled++;
+            return true;
+        };
+
+        expect([1].reduceRight(callback)).toBe(1);
+        expect(callbackCalled).toBe(0);
+
+        expect([1].reduceRight(callback)).toBe(1);
+        expect(callbackCalled).toBe(0);
+
+        callbackCalled = 0;
+        expect([1, 2, 3].reduceRight(callback)).toBe(true);
+        expect(callbackCalled).toBe(2);
+
+        callbackCalled = 0;
+        expect([1, 2, 3, ,].reduceRight(callback)).toBe(true);
+        expect(callbackCalled).toBe(2);
+
+        callbackCalled = 0;
+        expect([, , , 1, , , 10, , 100, , ,].reduceRight(callback)).toBe(true);
+        expect(callbackCalled).toBe(2);
+
+        var constantlySad = () => ":^(";
+        var result = [].reduceRight(constantlySad, ":^)");
+        expect(result).toBe(":^)");
+
+        result = [":^0"].reduceRight(constantlySad, ":^)");
+        expect(result).toBe(":^(");
+
+        result = [":^0"].reduceRight(constantlySad);
+        expect(result).toBe(":^0");
+
+        result = [5, 4, 3, 2, 1].reduceRight((accum, elem) => "" + accum + elem);
+        expect(result).toBe("12345");
+
+        result = [1, 2, 3, 4, 5, 6].reduceRight((accum, elem) => {
+            return "" + accum + elem;
+        }, 100);
+        expect(result).toBe("100654321");
+
+        result = [6, 5, 4, 3, 2, 1].reduceRight((accum, elem) => {
+            return "" + accum + elem;
+        }, 100);
+        expect(result).toBe("100123456");
+
+        var indexes = [];
+        result = ["foo", 1, true].reduceRight((a, v, i) => {
+            indexes.push(i);
+        });
+        expect(result).toBeUndefined();
+        expect(indexes.length).toBe(2);
+        expect(indexes[0]).toBe(1);
+        expect(indexes[1]).toBe(0);
+
+        indexes = [];
+        result = ["foo", 1, true].reduceRight((a, v, i) => {
+            indexes.push(i);
+        }, "foo");
+        expect(result).toBeUndefined();
+        expect(indexes).toEqual([2, 1, 0]);
+
+        var mutable = { prop: 0 };
+        result = ["foo", 1, true].reduceRight((a, v) => {
+            a.prop = v;
+            return a;
+        }, mutable);
+        expect(result).toBe(mutable);
+        expect(result.prop).toBe("foo");
+
+        var a1 = [1, 2];
+        var a2 = null;
+        a1.reduceRight((a, v, i, t) => {
+            a2 = t;
+        });
+        expect(a1).toBe(a2);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.reverse.js

@@ -0,0 +1,9 @@
+test("length is 0", () => {
+    expect(Array.prototype.reverse).toHaveLength(0);
+});
+
+test("basic functionality", () => {
+    var array = [1, 2, 3];
+    expect(array.reverse()).toEqual([3, 2, 1]);
+    expect(array).toEqual([3, 2, 1]);
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.shift.js

@@ -0,0 +1,23 @@
+test("length is 0", () => {
+    expect(Array.prototype.shift).toHaveLength(0);
+});
+
+describe("normal behavior", () => {
+    test("array with elements", () => {
+        var a = [1, 2, 3];
+        expect(a.shift()).toBe(1);
+        expect(a).toEqual([2, 3]);
+    });
+
+    test("empty array", () => {
+        var a = [];
+        expect(a.shift()).toBeUndefined();
+        expect(a).toEqual([]);
+    });
+
+    test("array with empty slot", () => {
+        var a = [,];
+        expect(a.shift()).toBeUndefined();
+        expect(a).toEqual([]);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.slice.js

@@ -0,0 +1,39 @@
+test("length is 0", () => {
+    expect(Array.prototype.slice).toHaveLength(2);
+});
+
+test("basic functionality", () => {
+    var array = ["hello", "friends", "serenity", 1];
+
+    var slice = array.slice();
+    expect(array).toEqual(["hello", "friends", "serenity", 1]);
+    expect(slice).toEqual(["hello", "friends", "serenity", 1]);
+
+    slice = array.slice(1);
+    expect(array).toEqual(["hello", "friends", "serenity", 1]);
+    expect(slice).toEqual(["friends", "serenity", 1]);
+
+    slice = array.slice(0, 2);
+    expect(array).toEqual(["hello", "friends", "serenity", 1]);
+    expect(slice).toEqual(["hello", "friends"]);
+
+    slice = array.slice(-1);
+    expect(array).toEqual(["hello", "friends", "serenity", 1]);
+    expect(slice).toEqual([1]);
+
+    slice = array.slice(1, 1);
+    expect(array).toEqual(["hello", "friends", "serenity", 1]);
+    expect(slice).toEqual([]);
+
+    slice = array.slice(1, -1);
+    expect(array).toEqual(["hello", "friends", "serenity", 1]);
+    expect(slice).toEqual(["friends", "serenity"]);
+
+    slice = array.slice(2, -1);
+    expect(array).toEqual(["hello", "friends", "serenity", 1]);
+    expect(slice).toEqual(["serenity"]);
+
+    slice = array.slice(0, 100);
+    expect(array).toEqual(["hello", "friends", "serenity", 1]);
+    expect(slice).toEqual(["hello", "friends", "serenity", 1]);
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.some.js

@@ -0,0 +1,37 @@
+test("length is 1", () => {
+    expect(Array.prototype.some).toHaveLength(1);
+});
+
+describe("errors", () => {
+    test("requires at least one argument", () => {
+        expect(() => {
+            [].some();
+        }).toThrowWithMessage(TypeError, "Array.prototype.some() requires at least one argument");
+    });
+
+    test("callback must be a function", () => {
+        expect(() => {
+            [].some(undefined);
+        }).toThrowWithMessage(TypeError, "undefined is not a function");
+    });
+});
+
+test("basic functionality", () => {
+    var array = ["hello", "friends", 1, 2, false, -42, { name: "serenityos" }];
+
+    expect(array.some(value => value === "hello")).toBeTrue();
+    expect(array.some(value => value === "serenity")).toBeFalse();
+    expect(array.some((value, index, arr) => index === 1)).toBeTrue();
+    expect(array.some(value => value == "1")).toBeTrue();
+    expect(array.some(value => value === 1)).toBeTrue();
+    expect(array.some(value => value === 13)).toBeFalse();
+    expect(array.some(value => typeof value !== "string")).toBeTrue();
+    expect(array.some(value => typeof value === "boolean")).toBeTrue();
+    expect(array.some(value => value > 1)).toBeTrue();
+    expect(array.some(value => value > 1 && value < 3)).toBeTrue();
+    expect(array.some(value => value > 100)).toBeFalse();
+    expect(array.some(value => value < 0)).toBeTrue();
+    expect(array.some(value => array.pop())).toBeTrue();
+    expect(["", "hello", "friends", "serenity"].some(value => value.length === 0)).toBeTrue();
+    expect([].some(value => value === 1)).toBeFalse();
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.sort.js

@@ -0,0 +1,204 @@
+describe("Array.prototype.sort", () => {
+    test("basic functionality", () => {
+        expect(Array.prototype.sort).toHaveLength(1);
+
+        var arr = ["c", "b", "d", "a"];
+        expect(arr.sort()).toEqual(arr);
+        expect(arr).toEqual(["a", "b", "c", "d"]);
+
+        arr = ["aa", "a"];
+        expect(arr.sort()).toEqual(arr);
+        expect(arr).toEqual(["a", "aa"]);
+
+        arr = [1, 0];
+        expect(arr.sort()).toBe(arr); // should be exactly same object
+        expect(arr).toEqual([0, 1]);
+
+        // numbers are sorted as strings
+        arr = [205, -123, 22, 200, 3, -20, -2, -1, 25, 2, 0, 1];
+        expect(arr.sort()).toEqual([-1, -123, -2, -20, 0, 1, 2, 200, 205, 22, 25, 3]);
+
+        // mix of data, including empty slots and undefined
+        arr = ["2", Infinity, null, null, , undefined, 5, , undefined, null, 54, "5"];
+        expect(arr.sort()).toEqual([
+            "2",
+            5,
+            "5",
+            54,
+            Infinity,
+            null,
+            null,
+            null,
+            undefined,
+            undefined,
+            ,
+            ,
+        ]);
+        expect(arr.length).toEqual(12);
+
+        // undefined compare function
+        arr = ["2", Infinity, null, null, , undefined, 5n, , undefined, null, 54, "5"];
+        expect(arr.sort(undefined)).toEqual([
+            "2",
+            5n,
+            "5",
+            54,
+            Infinity,
+            null,
+            null,
+            null,
+            undefined,
+            undefined,
+            ,
+            ,
+        ]);
+        expect(arr.length).toEqual(12);
+
+        // numeric data with compare function to sort numerically
+        arr = [50, 500, 5, Infinity, -Infinity, 0, 10, -10, 1, -1, 5, 0, 15, Infinity];
+        expect(arr.sort((a, b) => a - b)).toEqual([
+            -Infinity,
+            -10,
+            -1,
+            0,
+            0,
+            1,
+            5,
+            5,
+            10,
+            15,
+            50,
+            500,
+            Infinity,
+            Infinity,
+        ]);
+        expect(arr.length).toEqual(14);
+
+        // numeric data with compare function to sort reverse numerically
+        arr = [50, 500, 5, Infinity, -Infinity, 0, 10, -10, 1, -1, 5, 0, 15, Infinity];
+        expect(arr.sort((a, b) => b - a)).toEqual([
+            Infinity,
+            Infinity,
+            500,
+            50,
+            15,
+            10,
+            5,
+            5,
+            1,
+            0,
+            0,
+            -1,
+            -10,
+            -Infinity,
+        ]);
+
+        // small/edge cases
+        expect([].sort()).toEqual([]);
+        expect([5].sort()).toEqual([5]);
+        expect([5, 5].sort()).toEqual([5, 5]);
+        expect([undefined].sort()).toEqual([undefined]);
+        expect([undefined, undefined].sort()).toEqual([undefined, undefined]);
+        expect([,].sort()).toEqual([,]);
+        expect([, ,].sort()).toEqual([, ,]);
+        expect([5, ,].sort()).toEqual([5, ,]);
+        expect([, , 5].sort()).toEqual([5, , ,]);
+
+        // sorting should be stable
+        arr = [
+            { sorted_key: 2, other_property: 1 },
+            { sorted_key: 2, other_property: 2 },
+            { sorted_key: 1, other_property: 3 },
+        ];
+        arr.sort((a, b) => a.sorted_key - b.sorted_key);
+        expect(arr[1].other_property == 1);
+        expect(arr[2].other_property == 2);
+    });
+
+    test("that it makes no unnecessary calls to compare function", () => {
+        expectNoCallCompareFunction = function (a, b) {
+            expect().fail();
+        };
+
+        expect([].sort(expectNoCallCompareFunction)).toEqual([]);
+        expect([1].sort(expectNoCallCompareFunction)).toEqual([1]);
+        expect([1, undefined].sort(expectNoCallCompareFunction)).toEqual([1, undefined]);
+        expect([undefined, undefined].sort(expectNoCallCompareFunction)).toEqual([
+            undefined,
+            undefined,
+        ]);
+        expect([, , 1, ,].sort(expectNoCallCompareFunction)).toEqual([1, , , ,]);
+        expect([undefined, , 1, , undefined, ,].sort(expectNoCallCompareFunction)).toEqual([
+            1,
+            undefined,
+            undefined,
+            ,
+            ,
+            ,
+        ]);
+    });
+
+    test("that it works on non-arrays", () => {
+        var obj = { length: 0 };
+        expect(Array.prototype.sort.call(obj)).toBe(obj);
+        expect(obj).toEqual({ length: 0 });
+
+        obj = { 0: 1, length: 0 };
+        expect(Array.prototype.sort.call(obj, undefined)).toBe(obj);
+        expect(obj).toEqual({ 0: 1, length: 0 });
+
+        obj = { 0: 3, 1: 2, 2: 1, 3: 0, length: 2 };
+        expect(Array.prototype.sort.call(obj)).toBe(obj);
+        expect(obj).toEqual({ 0: 2, 1: 3, 2: 1, 3: 0, length: 2 });
+
+        obj = { 0: 3, 1: 2, 2: 1, a: "b", hello: "friends!", length: 2 };
+        expect(Array.prototype.sort.call(obj)).toBe(obj);
+        expect(obj).toEqual({ 0: 2, 1: 3, 2: 1, 3: 0, a: "b", hello: "friends!", length: 2 });
+
+        obj = { 0: 2, 1: 3, 2: 1, a: "b", hello: "friends!", length: 2 };
+        expect(
+            Array.prototype.sort.call(obj, (a, b) => {
+                expect(a == 2 || a == 3).toBeTrue();
+                expect(b == 2 || b == 3).toBeTrue();
+                return b - a;
+            })
+        ).toBe(obj);
+        expect(obj).toEqual({ 0: 3, 1: 2, 2: 1, 3: 0, a: "b", hello: "friends!", length: 2 });
+    });
+
+    test("that it handles abrupt completions correctly", () => {
+        class TestError extends Error {
+            constructor() {
+                super();
+                this.name = "TestError";
+            }
+        }
+
+        arr = [1, 2, 3];
+        expect(() =>
+            arr.sort((a, b) => {
+                throw new TestError();
+            })
+        ).toThrow(TestError);
+
+        class DangerousToString {
+            toString() {
+                throw new TestError();
+            }
+        }
+        arr = [new DangerousToString(), new DangerousToString()];
+        expect(() => arr.sort()).toThrow(TestError);
+    });
+
+    test("that it does not use deleteProperty unnecessarily", () => {
+        var obj = new Proxy(
+            { 0: 5, 1: 4, 2: 3, length: 3 },
+            {
+                deleteProperty: function (target, property) {
+                    expect().fail();
+                },
+            }
+        );
+        Array.prototype.sort.call(obj);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.splice.js

@@ -0,0 +1,49 @@
+test("length is 2", () => {
+    expect(Array.prototype.splice).toHaveLength(2);
+});
+
+test("basic functionality", () => {
+    var array = ["hello", "friends", "serenity", 1, 2];
+    var removed = array.splice(3);
+    expect(array).toEqual(["hello", "friends", "serenity"]);
+    expect(removed).toEqual([1, 2]);
+
+    array = ["hello", "friends", "serenity", 1, 2];
+    removed = array.splice(-2);
+    expect(array).toEqual(["hello", "friends", "serenity"]);
+    expect(removed).toEqual([1, 2]);
+
+    array = ["hello", "friends", "serenity", 1, 2];
+    removed = array.splice(-2, 1);
+    expect(array).toEqual(["hello", "friends", "serenity", 2]);
+    expect(removed).toEqual([1]);
+
+    array = ["serenity"];
+    removed = array.splice(0, 0, "hello", "friends");
+    expect(array).toEqual(["hello", "friends", "serenity"]);
+    expect(removed).toEqual([]);
+
+    array = ["goodbye", "friends", "serenity"];
+    removed = array.splice(0, 1, "hello");
+    expect(array).toEqual(["hello", "friends", "serenity"]);
+    expect(removed).toEqual(["goodbye"]);
+
+    array = ["foo", "bar", "baz"];
+    removed = array.splice();
+    expect(array).toEqual(["foo", "bar", "baz"]);
+    expect(removed).toEqual([]);
+
+    removed = array.splice(0, 123);
+    expect(array).toEqual([]);
+    expect(removed).toEqual(["foo", "bar", "baz"]);
+
+    array = ["foo", "bar", "baz"];
+    removed = array.splice(123, 123);
+    expect(array).toEqual(["foo", "bar", "baz"]);
+    expect(removed).toEqual([]);
+
+    array = ["foo", "bar", "baz"];
+    removed = array.splice(-123, 123);
+    expect(array).toEqual([]);
+    expect(removed).toEqual(["foo", "bar", "baz"]);
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.toLocaleString.js

@@ -0,0 +1,62 @@
+test("length is 0", () => {
+    expect(Array.prototype.toLocaleString).toHaveLength(0);
+});
+
+describe("normal behavior", () => {
+    test("array with no elements", () => {
+        expect([].toLocaleString()).toBe("");
+    });
+
+    test("array with one element", () => {
+        expect(["foo"].toLocaleString()).toBe("foo");
+    });
+
+    test("array with multiple elements", () => {
+        expect(["foo", "bar", "baz"].toLocaleString()).toBe("foo,bar,baz");
+    });
+
+    test("null and undefined result in empty strings", () => {
+        expect([null].toLocaleString()).toBe("");
+        expect([undefined].toLocaleString()).toBe("");
+        expect([undefined, null].toLocaleString()).toBe(",");
+    });
+
+    test("empty values result in empty strings", () => {
+        expect(new Array(1).toLocaleString()).toBe("");
+        expect(new Array(3).toLocaleString()).toBe(",,");
+        var a = new Array(5);
+        a[2] = "foo";
+        a[4] = "bar";
+        expect(a.toLocaleString()).toBe(",,foo,,bar");
+    });
+
+    test("getter property is included in returned string", () => {
+        var a = ["foo"];
+        Object.defineProperty(a, 1, {
+            get() {
+                return "bar";
+            },
+        });
+        expect(a.toLocaleString()).toBe("foo,bar");
+    });
+
+    test("array with elements that have a custom toString() function", () => {
+        var toStringCalled = 0;
+        var o = {
+            toString() {
+                toStringCalled++;
+                return "o";
+            },
+        };
+        expect([o, undefined, o, null, o].toLocaleString()).toBe("o,,o,,o");
+        expect(toStringCalled).toBe(3);
+    });
+
+    test("array with circular references", () => {
+        const a = ["foo", [], [1, 2, []], ["bar"]];
+        a[1] = a;
+        a[2][2] = a;
+        // [ "foo", <circular>, [ 1, 2, <circular> ], [ "bar" ] ]
+        expect(a.toLocaleString()).toBe("foo,,1,2,,bar");
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.toString.js

@@ -0,0 +1,66 @@
+test("length is 0", () => {
+    expect(Array.prototype.toString).toHaveLength(0);
+});
+
+describe("normal behavior", () => {
+    test("array with no elements", () => {
+        expect([].toString()).toBe("");
+    });
+
+    test("array with one element", () => {
+        expect([1].toString()).toBe("1");
+    });
+
+    test("array with multiple elements", () => {
+        expect([1, 2, 3].toString()).toBe("1,2,3");
+    });
+
+    test("string and array concatenation", () => {
+        expect("rgb(" + [10, 11, 12] + ")").toBe("rgb(10,11,12)");
+    });
+
+    test("null and undefined result in empty strings", () => {
+        expect([null].toString()).toBe("");
+        expect([undefined].toString()).toBe("");
+        expect([undefined, null].toString()).toBe(",");
+    });
+
+    test("empty values result in empty strings", () => {
+        expect(new Array(1).toString()).toBe("");
+        expect(new Array(3).toString()).toBe(",,");
+        var a = new Array(5);
+        a[2] = "foo";
+        a[4] = "bar";
+        expect(a.toString()).toBe(",,foo,,bar");
+    });
+
+    test("getter property is included in returned string", () => {
+        var a = [1, 2, 3];
+        Object.defineProperty(a, 3, {
+            get() {
+                return 10;
+            },
+        });
+        expect(a.toString()).toBe("1,2,3,10");
+    });
+
+    test("array with elements that have a custom toString() function", () => {
+        var toStringCalled = 0;
+        var o = {
+            toString() {
+                toStringCalled++;
+                return "o";
+            },
+        };
+        expect([o, undefined, o, null, o].toString()).toBe("o,,o,,o");
+        expect(toStringCalled).toBe(3);
+    });
+
+    test("array with circular references", () => {
+        const a = ["foo", [], [1, 2, []], ["bar"]];
+        a[1] = a;
+        a[2][2] = a;
+        // [ "foo", <circular>, [ 1, 2, <circular> ], [ "bar" ] ]
+        expect(a.toString()).toBe("foo,,1,2,,bar");
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.unshift.js

@@ -0,0 +1,23 @@
+test("length is 1", () => {
+    expect(Array.prototype.unshift).toHaveLength(1);
+});
+
+describe("normal behavior", () => {
+    test("no argument", () => {
+        var a = ["hello"];
+        expect(a.unshift()).toBe(1);
+        expect(a).toEqual(["hello"]);
+    });
+
+    test("single argument", () => {
+        var a = ["hello"];
+        expect(a.unshift("friends")).toBe(2);
+        expect(a).toEqual(["friends", "hello"]);
+    });
+
+    test("multiple arguments", () => {
+        var a = ["friends", "hello"];
+        expect(a.unshift(1, 2, 3)).toBe(5);
+        expect(a).toEqual([1, 2, 3, "friends", "hello"]);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/Array.prototype.values.js

@@ -0,0 +1,44 @@
+test("length", () => {
+    expect(Array.prototype.values.length).toBe(0);
+});
+
+test("basic functionality", () => {
+    const a = [1, 2, 3];
+    const it = a.values();
+    expect(it.next()).toEqual({ value: 1, done: false });
+    expect(it.next()).toEqual({ value: 2, done: false });
+    expect(it.next()).toEqual({ value: 3, done: false });
+    expect(it.next()).toEqual({ value: undefined, done: true });
+    expect(it.next()).toEqual({ value: undefined, done: true });
+    expect(it.next()).toEqual({ value: undefined, done: true });
+});
+
+test("works when applied to non-object", () => {
+    [true, false, 9, 2n, Symbol()].forEach(primitive => {
+        const it = [].values.call(primitive);
+        expect(it.next()).toEqual({ value: undefined, done: true });
+        expect(it.next()).toEqual({ value: undefined, done: true });
+        expect(it.next()).toEqual({ value: undefined, done: true });
+    });
+});
+
+test("item added to array before exhaustion is accessible", () => {
+    const a = [1, 2];
+    const it = a.values();
+    expect(it.next()).toEqual({ value: 1, done: false });
+    expect(it.next()).toEqual({ value: 2, done: false });
+    a.push(3);
+    expect(it.next()).toEqual({ value: 3, done: false });
+    expect(it.next()).toEqual({ value: undefined, done: true });
+    expect(it.next()).toEqual({ value: undefined, done: true });
+});
+
+test("item added to array after exhaustion is inaccessible", () => {
+    const a = [1, 2];
+    const it = a.values();
+    expect(it.next()).toEqual({ value: 1, done: false });
+    expect(it.next()).toEqual({ value: 2, done: false });
+    expect(it.next()).toEqual({ value: undefined, done: true });
+    a.push(3);
+    expect(it.next()).toEqual({ value: undefined, done: true });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/array-basic.js

@@ -0,0 +1,57 @@
+test("basic functionality", () => {
+    var a = [1, 2, 3];
+
+    expect(typeof a).toBe("object");
+    expect(a).toHaveLength(3);
+    expect(a[0]).toBe(1);
+    expect(a[1]).toBe(2);
+    expect(a[2]).toBe(3);
+
+    a[1] = 5;
+    expect(a[1]).toBe(5);
+    expect(a).toHaveLength(3);
+
+    a.push(7);
+    expect(a[3]).toBe(7);
+    expect(a).toHaveLength(4);
+
+    a = [,];
+    expect(a).toHaveLength(1);
+    expect(a.toString()).toBe("");
+    expect(a[0]).toBeUndefined();
+
+    a = [, , , ,];
+    expect(a).toHaveLength(4);
+    expect(a.toString()).toBe(",,,");
+    expect(a[0]).toBeUndefined();
+    expect(a[1]).toBeUndefined();
+    expect(a[2]).toBeUndefined();
+    expect(a[3]).toBeUndefined();
+
+    a = [1, , 2, , , 3];
+    expect(a).toHaveLength(6);
+    expect(a.toString()).toBe("1,,2,,,3");
+    expect(a[0]).toBe(1);
+    expect(a[1]).toBeUndefined();
+    expect(a[2]).toBe(2);
+    expect(a[3]).toBeUndefined();
+    expect(a[4]).toBeUndefined();
+    expect(a[5]).toBe(3);
+
+    a = [1, , 2, , , 3];
+    Object.defineProperty(a, 1, {
+        get() {
+            return this.getterSetterValue;
+        },
+        set(value) {
+            this.getterSetterValue = value;
+        },
+    });
+    expect(a).toHaveLength(6);
+    expect(a.toString()).toBe("1,,2,,,3");
+    expect(a.getterSetterValue).toBeUndefined();
+    a[1] = 20;
+    expect(a).toHaveLength(6);
+    expect(a.toString()).toBe("1,20,2,,,3");
+    expect(a.getterSetterValue).toBe(20);
+});

Userland/Libraries/LibJS/Tests/builtins/Array/array-length-setter.js

@@ -0,0 +1,37 @@
+describe("errors", () => {
+    test("invalid array length value", () => {
+        var a = [1, 2, 3];
+        [undefined, "foo", -1, Infinity, -Infinity, NaN].forEach(value => {
+            expect(() => {
+                a.length = value;
+            }).toThrowWithMessage(RangeError, "Invalid array length");
+            expect(a).toHaveLength(3);
+        });
+    });
+});
+
+describe("normal behavior", () => {
+    test("extend array by setting length", () => {
+        var a = [1, 2, 3];
+        a.length = 5;
+        expect(a).toEqual([1, 2, 3, undefined, undefined]);
+    });
+
+    test("truncate array by setting length", () => {
+        var a = [1, 2, 3];
+        a.length = 2;
+        expect(a).toEqual([1, 2]);
+        a.length = 0;
+        expect(a).toEqual([]);
+    });
+
+    test("length value is coerced to number if possible", () => {
+        var a = [1, 2, 3];
+        a.length = "42";
+        expect(a).toHaveLength(42);
+        a.length = [];
+        expect(a).toHaveLength(0);
+        a.length = true;
+        expect(a).toHaveLength(1);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/array-shrink-during-find-crash.js

@@ -0,0 +1,19 @@
+test("Issue #1992, shrinking array during find() iteration", () => {
+    var a, callbackCalled;
+
+    callbackCalled = 0;
+    a = [1, 2, 3, 4, 5];
+    a.find(() => {
+        callbackCalled++;
+        a.pop();
+    });
+    expect(callbackCalled).toBe(5);
+
+    callbackCalled = 0;
+    a = [1, 2, 3, 4, 5];
+    a.findIndex(() => {
+        callbackCalled++;
+        a.pop();
+    });
+    expect(callbackCalled).toBe(5);
+});

Userland/Libraries/LibJS/Tests/builtins/Array/array-simple-and-generic-storage-initialization.js

@@ -0,0 +1,15 @@
+describe("Issue #3382", () => {
+    test("Creating an array with simple storage (<= 200 initial elements)", () => {
+        var a = Array(200);
+        expect(a).toHaveLength(200);
+        expect(a.push("foo")).toBe(201);
+        expect(a).toHaveLength(201);
+    });
+
+    test("Creating an array with generic storage (> 200 initial elements)", () => {
+        var a = Array(201);
+        expect(a).toHaveLength(201);
+        expect(a.push("foo")).toBe(202);
+        expect(a).toHaveLength(202);
+    });
+});

Userland/Libraries/LibJS/Tests/builtins/Array/array-spread.js

@@ -0,0 +1,25 @@
+describe("errors", () => {
+    test("cannot spread number in array", () => {
+        expect(() => {
+            [...1];
+        }).toThrowWithMessage(TypeError, "1 is not iterable");
+    });
+
+    test("cannot spread object in array", () => {
+        expect(() => {
+            [...{}];
+        }).toThrowWithMessage(TypeError, "[object Object] is not iterable");
+    });
+});
+
+test("basic functionality", () => {
+    expect([1, ...[2, 3], 4]).toEqual([1, 2, 3, 4]);
+
+    let a = [2, 3];
+    expect([1, ...a, 4]).toEqual([1, 2, 3, 4]);
+
+    let obj = { a: [2, 3] };
+    expect([1, ...obj.a, 4]).toEqual([1, 2, 3, 4]);
+
+    expect([...[], ...[...[1, 2, 3]], 4]).toEqual([1, 2, 3, 4]);
+});