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LibJS: Implement Array.prototype.groupBy

This commit is contained in:
Luke Wilde 2022-01-05 00:29:27 +00:00 committed by Linus Groh
parent 4a14455dff
commit 48cc1c97d5
5 changed files with 202 additions and 1 deletions

View file

@ -304,4 +304,17 @@ describe("ability to work with generic non-array objects", () => {
2,
]);
});
test("groupBy", () => {
const visited = [];
const o = { length: 5, 0: "foo", 1: "bar", 3: "baz" };
const result = Array.prototype.groupBy.call(o, (value, _, object) => {
expect(object).toBe(o);
visited.push(value);
return value !== undefined ? value.startsWith("b") : false;
});
expect(visited).toEqual(["foo", "bar", undefined, "baz", undefined]);
expect(result.false).toEqual(["foo", undefined, undefined]);
expect(result.true).toEqual(["bar", "baz"]);
});
});

View file

@ -0,0 +1,101 @@
test("length is 1", () => {
expect(Array.prototype.groupBy).toHaveLength(1);
});
describe("errors", () => {
test("callback must be a function", () => {
expect(() => {
[].groupBy(undefined);
}).toThrowWithMessage(TypeError, "undefined is not a function");
});
test("null or undefined this value", () => {
expect(() => {
Array.prototype.groupBy.call();
}).toThrowWithMessage(TypeError, "ToObject on null or undefined");
expect(() => {
Array.prototype.groupBy.call(undefined);
}).toThrowWithMessage(TypeError, "ToObject on null or undefined");
expect(() => {
Array.prototype.groupBy.call(null);
}).toThrowWithMessage(TypeError, "ToObject on null or undefined");
});
});
describe("normal behavior", () => {
test("basic functionality", () => {
const array = [1, 2, 3, 4, 5, 6];
const visited = [];
const firstResult = array.groupBy(value => {
visited.push(value);
return value % 2 === 0;
});
expect(visited).toEqual([1, 2, 3, 4, 5, 6]);
expect(firstResult.true).toEqual([2, 4, 6]);
expect(firstResult.false).toEqual([1, 3, 5]);
const firstKeys = Object.keys(firstResult);
expect(firstKeys).toHaveLength(2);
expect(firstKeys[0]).toBe("false");
expect(firstKeys[1]).toBe("true");
const secondResult = array.groupBy((_, index) => {
return index < array.length / 2;
});
expect(secondResult.true).toEqual([1, 2, 3]);
expect(secondResult.false).toEqual([4, 5, 6]);
const secondKeys = Object.keys(secondResult);
expect(secondKeys).toHaveLength(2);
expect(secondKeys[0]).toBe("true");
expect(secondKeys[1]).toBe("false");
const thisArg = [7, 8, 9, 10, 11, 12];
const thirdResult = array.groupBy(function (_, __, arrayVisited) {
expect(arrayVisited).toBe(array);
expect(this).toBe(thisArg);
}, thisArg);
expect(thirdResult.undefined).not.toBe(array);
expect(thirdResult.undefined).not.toBe(thisArg);
expect(thirdResult.undefined).toEqual(array);
const thirdKeys = Object.keys(thirdResult);
expect(thirdKeys).toHaveLength(1);
expect(thirdKeys[0]).toBe("undefined");
});
test("is unscopable", () => {
expect(Array.prototype[Symbol.unscopables].groupBy).toBeTrue();
const array = [];
with (array) {
expect(() => {
groupBy;
}).toThrowWithMessage(ReferenceError, "'groupBy' is not defined");
}
});
test("never calls callback with empty array", () => {
var callbackCalled = 0;
expect(
[].groupBy(() => {
callbackCalled++;
})
).toEqual({});
expect(callbackCalled).toBe(0);
});
test("calls callback once for every item", () => {
var callbackCalled = 0;
const result = [1, 2, 3].groupBy(() => {
callbackCalled++;
});
expect(result.undefined).toEqual([1, 2, 3]);
expect(callbackCalled).toBe(3);
});
});