Iterator.from.js 2.9 KB

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  1. describe("errors", () => {
  2. test("called with non-Object", () => {
  3. expect(() => {
  4. Iterator.from(Symbol.hasInstance);
  5. }).toThrowWithMessage(TypeError, "obj is not an object");
  6. });
  7. test("@@iterator is not callable", () => {
  8. const iterable = {};
  9. iterable[Symbol.iterator] = 12389;
  10. expect(() => {
  11. Iterator.from(iterable);
  12. }).toThrowWithMessage(TypeError, "12389 is not a function");
  13. });
  14. test("@@iterator throws an exception", () => {
  15. function TestError() {}
  16. const iterable = {};
  17. iterable[Symbol.iterator] = () => {
  18. throw new TestError();
  19. };
  20. expect(() => {
  21. Iterator.from(iterable);
  22. }).toThrow(TestError);
  23. });
  24. test("@@iterator return a non-Object", () => {
  25. const iterable = {};
  26. iterable[Symbol.iterator] = () => {
  27. return Symbol.hasInstance;
  28. };
  29. expect(() => {
  30. Iterator.from(iterable);
  31. }).toThrowWithMessage(TypeError, "iterator is not an object");
  32. });
  33. });
  34. describe("normal behavior", () => {
  35. test("length is 1", () => {
  36. expect(Iterator.from).toHaveLength(1);
  37. });
  38. test("create Iterator from a string", () => {
  39. const iterator = Iterator.from("ab");
  40. let result = iterator.next();
  41. expect(result.value).toBe("a");
  42. expect(result.done).toBeFalse();
  43. result = iterator.next();
  44. expect(result.value).toBe("b");
  45. expect(result.done).toBeFalse();
  46. result = iterator.next();
  47. expect(result.value).toBeUndefined();
  48. expect(result.done).toBeTrue();
  49. });
  50. test("create Iterator from generator", () => {
  51. function* generator() {
  52. yield 1;
  53. yield 2;
  54. }
  55. const iterator = Iterator.from(generator());
  56. let result = iterator.next();
  57. expect(result.value).toBe(1);
  58. expect(result.done).toBeFalse();
  59. result = iterator.next();
  60. expect(result.value).toBe(2);
  61. expect(result.done).toBeFalse();
  62. result = iterator.next();
  63. expect(result.value).toBeUndefined();
  64. expect(result.done).toBeTrue();
  65. });
  66. test("create Iterator from iterator-like object", () => {
  67. class TestIterator {
  68. next() {
  69. if (this.#first) {
  70. this.#first = false;
  71. return { value: 1, done: false };
  72. }
  73. return { value: undefined, done: true };
  74. }
  75. #first = true;
  76. }
  77. const testIterator = new TestIterator();
  78. const iterator = Iterator.from(testIterator);
  79. let result = iterator.next();
  80. expect(result.value).toBe(1);
  81. expect(result.done).toBeFalse();
  82. result = iterator.next();
  83. expect(result.value).toBeUndefined();
  84. expect(result.done).toBeTrue();
  85. });
  86. });