javascript - 尝试从 javascript 中的异步调用创建数组时的回调

Question

我正在尝试使用一个使用 for 循环的函数从异步 get 请求创建一个数组，以便在 get 请求中传递参数。

var loadRarity = function () {

       var rarities = [];

       for (var i =0; i < deck.length; i++) {

           Card.get({cardName: deck[i].card_name}, function(data) {

               rarities.push(data.data[0].rarity);
               console.log(rarities); //20 instances where the array is being populated

            });   
        console.log(rarities);// result :20x [] empty array
        }
        return rarities;

 };
 var raritiesArray = loadRarity();
 console.log(raritiesArray); //empty array

我不知道如何使用回调来完成这项工作。

Answer 1

一个选项是增加一个计数器来检查您是否处于最后一个回调，然后在最后一个回调中执行任何所需的操作

var loadRarity = function () {

       var rarities = [];

       var counter = 0; // initialize counter

       for (var i =0; i < deck.length; i++) {

           Card.get({cardName: deck[i].card_name}, function(data) {

               counter += 1; //increment counter

               rarities.push(data.data[0].rarity);
               console.log(rarities); //20 instances where the array is being populated

               if(counter == deck.length){ //if true you are in the last callback
                 console.log(raritiesArray); // array with all the elements
               }

            });   
        }
        return rarities;

 };
 var raritiesArray = loadRarity();