javascript - 如何检查 Javascript Promise 是否已经实现？

Question

我修改了这个example通过添加循环和 Deferred 对象来了解所有的 promise 都已实现。

我想做的是将所有的 promise 放入一个数组中，并在所有 promise 都实现时打印出来。

这是我的代码:

get_data();

function get_data() {


  var myPromise = [];
  var calls = [];
  var resultset = '';
  for (var j = 0, k = 5; j < k; j++) {
    var d = $.Deferred();
    var p = get_result();
    if (p.isPending()) {
      console.log('pending');
    }
    p.then(function(resultset) {
      if (p.isFulfilled()) {
        myPromise.push(resultset);
        calls.push(d);
      }
    });

  }

  $.when.apply($, calls).then(function() {
    console.log(myPromise); // always prints an empty array.
  });
}

function get_result() {

  return MakeQuerablePromise(new Promise(function(result, reject) {
    setTimeout(function() {
      result("Yeah !");
    }, 10000);
  }));
}

Fiddle完整代码

Answer 1

来自 MDN :

The Promise.all(iterable) method returns a single Promise that resolves when all of the promises in the iterable argument have resolved or when the iterable argument contains no promises. It rejects with the reason of the first promise that rejects.

var p1 = Promise.resolve(3);
var p2 = 1337;
var p3 = new Promise((resolve, reject) => {
   setTimeout(resolve, 100, 'foo');
}); 

Promise.all([p1, p2, p3]).then(values => { 
  console.log(values); // [3, 1337, "foo"] 
});