d9d245faa7
Iterator.from creates an Iterator from either an existing iterator or an iterator-like object. In the latter case, it sets the prototype of the returned iterator to WrapForValidIteratorPrototype to wrap around the iterator-like object's iteration methods.
109 lines
2.9 KiB
JavaScript
109 lines
2.9 KiB
JavaScript
describe("errors", () => {
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test("called with non-Object", () => {
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expect(() => {
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Iterator.from(Symbol.hasInstance);
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}).toThrowWithMessage(TypeError, "obj is not an object");
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});
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test("@@iterator is not callable", () => {
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const iterable = {};
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iterable[Symbol.iterator] = 12389;
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expect(() => {
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Iterator.from(iterable);
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}).toThrowWithMessage(TypeError, "12389 is not a function");
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});
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test("@@iterator throws an exception", () => {
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function TestError() {}
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const iterable = {};
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iterable[Symbol.iterator] = () => {
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throw new TestError();
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};
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expect(() => {
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Iterator.from(iterable);
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}).toThrow(TestError);
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});
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test("@@iterator return a non-Object", () => {
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const iterable = {};
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iterable[Symbol.iterator] = () => {
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return Symbol.hasInstance;
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};
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expect(() => {
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Iterator.from(iterable);
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}).toThrowWithMessage(TypeError, "iterator is not an object");
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});
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});
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describe("normal behavior", () => {
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test("length is 1", () => {
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expect(Iterator.from).toHaveLength(1);
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});
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test("create Iterator from a string", () => {
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const iterator = Iterator.from("ab");
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let result = iterator.next();
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expect(result.value).toBe("a");
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expect(result.done).toBeFalse();
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result = iterator.next();
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expect(result.value).toBe("b");
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expect(result.done).toBeFalse();
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result = iterator.next();
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expect(result.value).toBeUndefined();
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expect(result.done).toBeTrue();
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});
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test("create Iterator from generator", () => {
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function* generator() {
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yield 1;
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yield 2;
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}
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const iterator = Iterator.from(generator());
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let result = iterator.next();
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expect(result.value).toBe(1);
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expect(result.done).toBeFalse();
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result = iterator.next();
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expect(result.value).toBe(2);
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expect(result.done).toBeFalse();
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result = iterator.next();
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expect(result.value).toBeUndefined();
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expect(result.done).toBeTrue();
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});
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test("create Iterator from iterator-like object", () => {
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class TestIterator {
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next() {
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if (this.#first) {
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this.#first = false;
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return { value: 1, done: false };
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}
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return { value: undefined, done: true };
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}
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#first = true;
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}
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const testIterator = new TestIterator();
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const iterator = Iterator.from(testIterator);
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let result = iterator.next();
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expect(result.value).toBe(1);
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expect(result.done).toBeFalse();
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result = iterator.next();
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expect(result.value).toBeUndefined();
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expect(result.done).toBeTrue();
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});
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});
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