describe("correct behavior", () => { test("numeric indexing", () => { const o = { 1: 23 }; expect(o[1]).toBe(23); expect(o[1n]).toBe(23); expect(o["1"]).toBe(23); o[10] = "123"; expect(o[10]).toBe("123"); expect(o["10"]).toBe("123"); o[10n] = "1234"; expect(o[10]).toBe("1234"); expect(o["10"]).toBe("1234"); }); test("string indexing", () => { let foo = "bar"; const o = { foo, bar: "baz", qux: true ? 10 : 20, hello: "friends", }; expect(o.foo).toBe("bar"); expect(o["foo"]).toBe("bar"); expect(o.qux).toBe(10), expect(o.hello).toBe("friends"); expect(o["hello"]).toBe("friends"); }); test("symbol keys", () => { let object = {}; let symbol = Symbol("foo"); object[symbol] = 2; expect(object[symbol]).toBe(2); }); test("numeric keys", () => { const hex = { 0x10: "16" }; const oct = { 0o10: "8" }; const bin = { 0b10: "2" }; const float = { 0.5: "0.5" }; expect(hex["16"]).toBe("16"); expect(oct["8"]).toBe("8"); expect(bin["2"]).toBe("2"); expect(float["0.5"]).toBe("0.5"); }); test("computed properties", () => { const foo = "bar"; const computed = "computed"; const o = { [1 + 2]: 42, [`I am a ${computed} key`]: foo, }; expect(o[3]).toBe(42); expect(o["I am a computed key"]).toBe("bar"); }); test("duplicate keys", () => { const o = { duplicate: "hello", duplicate: "world", }; expect(o.duplicate).toBe("world"); }); test("assigning after creation", () => { const o = {}; o.baz = "test"; expect(o.baz).toBe("test"); expect(o["baz"]).toBe("test"); expect(o[-1]).toBeUndefined(); o[-1] = "hello friends"; expect(o[-1]).toBe("hello friends"); expect(o["-1"]).toBe("hello friends"); }); test("floating point keys", () => { const math = { 3.14: "pi" }; expect(math["3.14"]).toBe("pi"); expect(math[3.14]).toBe("pi"); }); test("keywords as property keys", () => { const o2 = { return: 1, yield: 1, for: 1, catch: 1, break: 1, }; expect(o2.return).toBe(1); expect(o2.yield).toBe(1); expect(o2.for).toBe(1); expect(o2.catch).toBe(1); expect(o2.break).toBe(1); }); test("prototypical inheritance", () => { var base = { getNumber() { return 10; }, }; var derived = { getNumber() { return 20 + super.getNumber(); }, }; Object.setPrototypeOf(derived, base); expect(derived.getNumber()).toBe(30); }); }); describe("side effects", () => { let a; const append = x => { a.push(x); }; test("computed key side effects", () => { a = []; const o3 = { [append(1)]: 1, [append(2)]: 2, [append(3)]: 3 }; expect(a).toHaveLength(3); expect(a[0]).toBe(1); expect(a[1]).toBe(2); expect(a[2]).toBe(3); expect(o3.undefined).toBe(3); }); test("value side effects", () => { a = []; const o4 = { test: append(1), test: append(2), test: append(3) }; expect(a).toHaveLength(3); expect(a[0]).toBe(1); expect(a[1]).toBe(2); expect(a[2]).toBe(3); expect(o4.test).toBeUndefined(); }); }); describe("shorthanded properties with special names", () => { test("keywords cannot be used", () => { expect("({ function, })").not.toEval(); expect("({ var, })").not.toEval(); expect("({ const, })").not.toEval(); expect("({ class, })").not.toEval(); }); test("reserved words are allowed in non-strict mode", () => { { var implements = 3; expect({ implements }).toEqual({ implements: 3 }); } { var public = "a"; expect({ public }).toEqual({ public: "a" }); } { var let = 9; expect({ let }).toEqual({ let: 9 }); } { var await = 8; expect({ await }).toEqual({ await: 8 }); } { var async = 7; expect({ async }).toEqual({ async: 7 }); } { var yield = 6; expect({ yield }).toEqual({ yield: 6 }); } }); test("reserved words are not allowed in strict mode", () => { expect('"use strict"; var implements = 3; ({ implements })').not.toEval(); expect("\"use strict\"; var public = 'a'; ({ public })").not.toEval(); expect('"use strict"; var let = 9; ({ let, })').not.toEval(); expect('"use strict"; var yield = 6; ({ yield, })').not.toEval(); }); test("special non reserved words are allowed even in strict mode", () => { expect('"use strict"; var await = 8; ({ await, })').toEval(); expect('"use strict"; var async = 7; ({ async, })').toEval(); }); }); describe("errors", () => { test("syntax errors", () => { expect("({ foo: function() { super.bar; } })").not.toEval(); expect("({ get ...foo })").not.toEval(); expect("({ get... foo })").not.toEval(); expect("({ get foo })").not.toEval(); expect("({ get foo: bar })").not.toEval(); expect("({ get [foo]: bar })").not.toEval(); expect("({ get ...[foo] })").not.toEval(); expect("({ get foo(bar) {} })").not.toEval(); expect("({ set foo() {} })").not.toEval(); expect("({ set foo(...bar) {} })").not.toEval(); expect("({ set foo(bar, baz) {} })").not.toEval(); expect("({ ...foo: bar })").not.toEval(); }); });