最简版 promise.any， 实现方式令人拍手称绝
ES6 promises don't provide any(). A small library to implement them. Will convert arguments to promises if not already a promise.
var promiseAny = require('promise-any');
promiseAny([
Promise.reject('✗'),
Promise.resolve('✓'),
]).then(function(value) {
// value is '✓' :)
});
promiseAny([
Promise.reject('✗'),
Promise.reject('✗'),
]).catch(function(reasons) {
// reasons is ['✗', '✗'] :(
});Promise.any = arr => {
let reverse = promise => new Promise((resolve, reject) => Promise.resolve(promise).then(reject, resolve));
return reverse(Promise.all(arr.map(reverse)));
};
var fn1 = new Promise((resolve, reject) => {
setTimeout(resolve,1000,'a-1000');
});
var fn2 = new Promise((resolve, reject) => {
setTimeout(resolve,900,'a-900');
});
var fn3 = new Promise((resolve, reject) => {
setTimeout(reject,300,'a-300');
});
Promise.any([
fn1,fn2,fn3
]).then(function(value) {
console.log(value) //'a-900'
});
Promise.any 只对第一个实现很感兴趣，
这点不同于 Promise.race
Promise.race([
fn1,fn2,fn3
]).catch(function(value) {
console.log(value) //'a-300'
});
Promise.race对第一个返回感兴趣，但是第一个返回可能是 reject状态的，所以从某种意义上来说， 不如promise.any实际意义更大。虽然Promise.race已经被部分内核实现，而Promise.any仍然处于草案