LibJS: Add the Map built-in object

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

@@ -0,0 +1,45 @@
+test("constructor properties", () => {
+    expect(Map).toHaveLength(0);
+    expect(Map.name).toBe("Map");
+});
+
+describe("errors", () => {
+    test("invalid array iterators", () => {
+        [-100, Infinity, NaN, {}, 152n].forEach(value => {
+            expect(() => {
+                new Map(value);
+            }).toThrowWithMessage(TypeError, "is not iterable");
+        });
+    });
+    test("invalid iterator entries", () => {
+        expect(() => {
+            new Map([1, 2, 3]);
+        }).toThrowWithMessage(TypeError, "Iterator value 1 is not an object");
+    });
+    test("called without new", () => {
+        expect(() => {
+            Map();
+        }).toThrowWithMessage(TypeError, "Map constructor must be called with 'new'");
+    });
+});
+
+describe("normal behavior", () => {
+    test("typeof", () => {
+        expect(typeof new Map()).toBe("object");
+    });
+
+    test("constructor with single entries array argument", () => {
+        var a = new Map([
+            ["a", 0],
+            ["b", 1],
+            ["c", 2],
+        ]);
+        expect(a instanceof Map).toBeTrue();
+        expect(a).toHaveSize(3);
+        var seen = [false, false, false];
+        a.forEach(v => {
+            seen[v] = true;
+        });
+        expect(seen[0] && seen[1] && seen[2]);
+    });
+});