Question

我是javascript的相对新手，我正在尝试在for循环中进行多个ajax调用。它在每次循环时使用不同的url为ajax调用循环遍历数组的元素。问题是变量'test'的值总是等于“condition4”。我习惯了其他语言，其中'test'的值将是“condition1”，然后是“condition2”等，因为它通过for循环。这是我的代码的简化版本：

var myData = [];
var cnt = 0;
var link;
var myCounter = 0;
var myArray = ["condition1", "condition2", "condition3", "condition4"];

for (x = 0; x < myArray.length; x++) {
    link = "https://test.com/" + myArray[x];
    myCounter = x;
    GetJSON(function (results) {
        for (i = 0; i < results.data.length; i++) {
            var id = results.data[i].identifier;
            var test = myArray[myCounter];
            myData[cnt] = { "id": id, "test": test };
            cnt++;
        }
    });
}

function GetJSON(callback) {
    $.ajax({
        url: link,
        type: 'GET',
        dataType: 'json',
        success: function (results) {
            callback(results);
        }
    });
}

Answer 1

执行循环时，它会附加myCounter引用。然后，由于异步任务，当它完成并调用“myCounter”时，它已经达到了数字4.因此，当它调用“myCounter”时，它就是4.要隔离在范围内，您需要在每次迭代时创建一个新范围并隔离＆＃39; myCounter＆＃39;

的每个值

＆＃13;

for (x = 0; x < myArray.length; x++) {
    link = "https://test.com/" + myArray[x];
    myCounter = x;
    //IIFE
    (function() {
      var ownCounter = myCounter; //Isolating counter
      GetJSON(function (results) {
        for (i = 0; i < results.data.length; i++) {
            var id = results.data[i].identifier;
            var test = myArray[ownCounter];
            myData[cnt] = { "id": id, "test": test };
            cnt++;
        }
      });
      
    })();
    
}

＆＃13;

或者...

＆＃13;

for (let x = 0; x < myArray.length; x++) {
    link = "https://test.com/" + myArray[x];
    myCounter = x;
    
    GetJSON(function (results) {
      for (i = 0; i < results.data.length; i++) {
          var id = results.data[i].identifier;
          var test = myArray[x];
          myData[cnt] = { "id": id, "test": test };
          cnt++;
      }
    });
     
        
}

＆＃13;

Answer 2

我认为您可以通过向服务器发送和接收myCounter值来解决此问题

＆＃13;

for (x = 0; x < myArray.length; x++) {
  link = "https://test.com/" + myArray[x];
  myCounter = x;
  $.ajax({
    url: link,
    type: 'GET',
    dataType: 'json',
    data: { myCounter: myCounter}
    success: function(results) {
      for (i = 0; i < results.data.length; i++) {
        var id = results.data[i].identifier;
        var test = results.data[i].myCounter
        myData[cnt] = {
          "id": id,
          "test": test
        };
        cnt++;
      }
    }
  });

}

＆＃13;

在for循环中进行多个ajax调用

2 个答案: