Experimental port to Firebase hosting
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public/es6-promise@4.2.5/lib/es6-promise/promise/race.js
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84
public/es6-promise@4.2.5/lib/es6-promise/promise/race.js
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import {
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isArray
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} from "../utils";
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/**
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`Promise.race` returns a new promise which is settled in the same way as the
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first passed promise to settle.
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Example:
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```javascript
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let promise1 = new Promise(function(resolve, reject){
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setTimeout(function(){
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resolve('promise 1');
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}, 200);
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});
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let promise2 = new Promise(function(resolve, reject){
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setTimeout(function(){
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resolve('promise 2');
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}, 100);
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});
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Promise.race([promise1, promise2]).then(function(result){
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// result === 'promise 2' because it was resolved before promise1
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// was resolved.
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});
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```
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`Promise.race` is deterministic in that only the state of the first
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settled promise matters. For example, even if other promises given to the
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`promises` array argument are resolved, but the first settled promise has
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become rejected before the other promises became fulfilled, the returned
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promise will become rejected:
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```javascript
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let promise1 = new Promise(function(resolve, reject){
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setTimeout(function(){
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resolve('promise 1');
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}, 200);
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});
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let promise2 = new Promise(function(resolve, reject){
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setTimeout(function(){
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reject(new Error('promise 2'));
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}, 100);
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});
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Promise.race([promise1, promise2]).then(function(result){
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// Code here never runs
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}, function(reason){
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// reason.message === 'promise 2' because promise 2 became rejected before
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// promise 1 became fulfilled
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});
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```
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An example real-world use case is implementing timeouts:
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```javascript
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Promise.race([ajax('foo.json'), timeout(5000)])
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```
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@method race
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@static
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@param {Array} promises array of promises to observe
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Useful for tooling.
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@return {Promise} a promise which settles in the same way as the first passed
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promise to settle.
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*/
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export default function race(entries) {
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/*jshint validthis:true */
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let Constructor = this;
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if (!isArray(entries)) {
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return new Constructor((_, reject) => reject(new TypeError('You must pass an array to race.')));
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} else {
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return new Constructor((resolve, reject) => {
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let length = entries.length;
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for (let i = 0; i < length; i++) {
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Constructor.resolve(entries[i]).then(resolve, reject);
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}
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});
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}
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}
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