index.js 6.8 KB

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  1. 'use strict';
  2. var immediate = require('immediate');
  3. /* istanbul ignore next */
  4. function INTERNAL() {}
  5. var handlers = {};
  6. var REJECTED = ['REJECTED'];
  7. var FULFILLED = ['FULFILLED'];
  8. var PENDING = ['PENDING'];
  9. /* istanbul ignore else */
  10. if (!process.browser) {
  11. // in which we actually take advantage of JS scoping
  12. var UNHANDLED = ['UNHANDLED'];
  13. }
  14. module.exports = Promise;
  15. function Promise(resolver) {
  16. if (typeof resolver !== 'function') {
  17. throw new TypeError('resolver must be a function');
  18. }
  19. this.state = PENDING;
  20. this.queue = [];
  21. this.outcome = void 0;
  22. /* istanbul ignore else */
  23. if (!process.browser) {
  24. this.handled = UNHANDLED;
  25. }
  26. if (resolver !== INTERNAL) {
  27. safelyResolveThenable(this, resolver);
  28. }
  29. }
  30. Promise.prototype.finally = function (callback) {
  31. if (typeof callback !== 'function') {
  32. return this;
  33. }
  34. var p = this.constructor;
  35. return this.then(resolve, reject);
  36. function resolve(value) {
  37. function yes () {
  38. return value;
  39. }
  40. return p.resolve(callback()).then(yes);
  41. }
  42. function reject(reason) {
  43. function no () {
  44. throw reason;
  45. }
  46. return p.resolve(callback()).then(no);
  47. }
  48. };
  49. Promise.prototype.catch = function (onRejected) {
  50. return this.then(null, onRejected);
  51. };
  52. Promise.prototype.then = function (onFulfilled, onRejected) {
  53. if (typeof onFulfilled !== 'function' && this.state === FULFILLED ||
  54. typeof onRejected !== 'function' && this.state === REJECTED) {
  55. return this;
  56. }
  57. var promise = new this.constructor(INTERNAL);
  58. /* istanbul ignore else */
  59. if (!process.browser) {
  60. if (this.handled === UNHANDLED) {
  61. this.handled = null;
  62. }
  63. }
  64. if (this.state !== PENDING) {
  65. var resolver = this.state === FULFILLED ? onFulfilled : onRejected;
  66. unwrap(promise, resolver, this.outcome);
  67. } else {
  68. this.queue.push(new QueueItem(promise, onFulfilled, onRejected));
  69. }
  70. return promise;
  71. };
  72. function QueueItem(promise, onFulfilled, onRejected) {
  73. this.promise = promise;
  74. if (typeof onFulfilled === 'function') {
  75. this.onFulfilled = onFulfilled;
  76. this.callFulfilled = this.otherCallFulfilled;
  77. }
  78. if (typeof onRejected === 'function') {
  79. this.onRejected = onRejected;
  80. this.callRejected = this.otherCallRejected;
  81. }
  82. }
  83. QueueItem.prototype.callFulfilled = function (value) {
  84. handlers.resolve(this.promise, value);
  85. };
  86. QueueItem.prototype.otherCallFulfilled = function (value) {
  87. unwrap(this.promise, this.onFulfilled, value);
  88. };
  89. QueueItem.prototype.callRejected = function (value) {
  90. handlers.reject(this.promise, value);
  91. };
  92. QueueItem.prototype.otherCallRejected = function (value) {
  93. unwrap(this.promise, this.onRejected, value);
  94. };
  95. function unwrap(promise, func, value) {
  96. immediate(function () {
  97. var returnValue;
  98. try {
  99. returnValue = func(value);
  100. } catch (e) {
  101. return handlers.reject(promise, e);
  102. }
  103. if (returnValue === promise) {
  104. handlers.reject(promise, new TypeError('Cannot resolve promise with itself'));
  105. } else {
  106. handlers.resolve(promise, returnValue);
  107. }
  108. });
  109. }
  110. handlers.resolve = function (self, value) {
  111. var result = tryCatch(getThen, value);
  112. if (result.status === 'error') {
  113. return handlers.reject(self, result.value);
  114. }
  115. var thenable = result.value;
  116. if (thenable) {
  117. safelyResolveThenable(self, thenable);
  118. } else {
  119. self.state = FULFILLED;
  120. self.outcome = value;
  121. var i = -1;
  122. var len = self.queue.length;
  123. while (++i < len) {
  124. self.queue[i].callFulfilled(value);
  125. }
  126. }
  127. return self;
  128. };
  129. handlers.reject = function (self, error) {
  130. self.state = REJECTED;
  131. self.outcome = error;
  132. /* istanbul ignore else */
  133. if (!process.browser) {
  134. if (self.handled === UNHANDLED) {
  135. immediate(function () {
  136. if (self.handled === UNHANDLED) {
  137. process.emit('unhandledRejection', error, self);
  138. }
  139. });
  140. }
  141. }
  142. var i = -1;
  143. var len = self.queue.length;
  144. while (++i < len) {
  145. self.queue[i].callRejected(error);
  146. }
  147. return self;
  148. };
  149. function getThen(obj) {
  150. // Make sure we only access the accessor once as required by the spec
  151. var then = obj && obj.then;
  152. if (obj && (typeof obj === 'object' || typeof obj === 'function') && typeof then === 'function') {
  153. return function appyThen() {
  154. then.apply(obj, arguments);
  155. };
  156. }
  157. }
  158. function safelyResolveThenable(self, thenable) {
  159. // Either fulfill, reject or reject with error
  160. var called = false;
  161. function onError(value) {
  162. if (called) {
  163. return;
  164. }
  165. called = true;
  166. handlers.reject(self, value);
  167. }
  168. function onSuccess(value) {
  169. if (called) {
  170. return;
  171. }
  172. called = true;
  173. handlers.resolve(self, value);
  174. }
  175. function tryToUnwrap() {
  176. thenable(onSuccess, onError);
  177. }
  178. var result = tryCatch(tryToUnwrap);
  179. if (result.status === 'error') {
  180. onError(result.value);
  181. }
  182. }
  183. function tryCatch(func, value) {
  184. var out = {};
  185. try {
  186. out.value = func(value);
  187. out.status = 'success';
  188. } catch (e) {
  189. out.status = 'error';
  190. out.value = e;
  191. }
  192. return out;
  193. }
  194. Promise.resolve = resolve;
  195. function resolve(value) {
  196. if (value instanceof this) {
  197. return value;
  198. }
  199. return handlers.resolve(new this(INTERNAL), value);
  200. }
  201. Promise.reject = reject;
  202. function reject(reason) {
  203. var promise = new this(INTERNAL);
  204. return handlers.reject(promise, reason);
  205. }
  206. Promise.all = all;
  207. function all(iterable) {
  208. var self = this;
  209. if (Object.prototype.toString.call(iterable) !== '[object Array]') {
  210. return this.reject(new TypeError('must be an array'));
  211. }
  212. var len = iterable.length;
  213. var called = false;
  214. if (!len) {
  215. return this.resolve([]);
  216. }
  217. var values = new Array(len);
  218. var resolved = 0;
  219. var i = -1;
  220. var promise = new this(INTERNAL);
  221. while (++i < len) {
  222. allResolver(iterable[i], i);
  223. }
  224. return promise;
  225. function allResolver(value, i) {
  226. self.resolve(value).then(resolveFromAll, function (error) {
  227. if (!called) {
  228. called = true;
  229. handlers.reject(promise, error);
  230. }
  231. });
  232. function resolveFromAll(outValue) {
  233. values[i] = outValue;
  234. if (++resolved === len && !called) {
  235. called = true;
  236. handlers.resolve(promise, values);
  237. }
  238. }
  239. }
  240. }
  241. Promise.race = race;
  242. function race(iterable) {
  243. var self = this;
  244. if (Object.prototype.toString.call(iterable) !== '[object Array]') {
  245. return this.reject(new TypeError('must be an array'));
  246. }
  247. var len = iterable.length;
  248. var called = false;
  249. if (!len) {
  250. return this.resolve([]);
  251. }
  252. var i = -1;
  253. var promise = new this(INTERNAL);
  254. while (++i < len) {
  255. resolver(iterable[i]);
  256. }
  257. return promise;
  258. function resolver(value) {
  259. self.resolve(value).then(function (response) {
  260. if (!called) {
  261. called = true;
  262. handlers.resolve(promise, response);
  263. }
  264. }, function (error) {
  265. if (!called) {
  266. called = true;
  267. handlers.reject(promise, error);
  268. }
  269. });
  270. }
  271. }