如何从javascript中的回调函数中获取完整数据

我编写了以下函数，它从 url 获取 json 数据。

function getWeatherDataForCities(cityArray){
  var arrAllrecords = [];
  var toDaysTimestamp = Math.round((new Date()).getTime() / 1000) - (24*60*60);
  for(var i in cityArray){

    for(var j=1; j<=2; j++){
        var jsonurl = "http://api.openweathermap.org/data/2.5/history/city?q="+cityArray[i]+"&dt="+toDaysTimestamp;

        $.ajax({
            url: jsonurl,
            dataType: "jsonp",
            mimeType: "textPlain",
            crossDomain: true,
            contentType: "application/json; charset=utf-8",
            success: function(data){
              arrAllrecords[j]["cityName"] = data.list[0].city.name;
              arrAllrecords[j]["weather"] = data.list[0].weather[0].description;

        } });
        toDaysTimestamp = toDaysTimestamp - (24*60*60);
    }   
  }

  return arrAllrecords;  //returning arrAllrecords
}

$(document ).ready(function() {

  var cityArray = new Array();
  cityArray[0] = "pune";
  var arrAllRecords = getWeatherDataForCities(cityArray);
  //Print All records returned by getWeatherDataForCities(cityArray);
});

我在上面的代码中写了一些注释。我已经调用getWeatherDataForCities function返回所有记录url.我已声明getWeatherDataForCities array在函数中。我想添加该数组中的所有返回记录。我已按照上面的方法尝试过，但没有任何内容进入array.

在控制台中显示 j 和 arrAllrecords 未定义。

如何从回调函数中获取数组中的所有记录？

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Your getWeatherDataForCities函数不会返回任何内容，因为 ajax 操作是异步的。您需要为此使用回调。

修改您的函数以接受回调函数：

function getWeatherDataForCities(cityArray, callback){
    var arrAllrecords = [];
    var toDaysTimestamp = Math.round((new Date()).getTime() / 1000) - (24*60*60);
    for(var i in cityArray){

       for(var j=1; j<=2; j++){
           var jsonurl = "http://api.openweathermap.org/data/2.5/history/city?q="+cityArray[i]+"&dt="+toDaysTimestamp;

            $.ajax({
                url: jsonurl,
                dataType: "jsonp",
                mimeType: "textPlain",
                crossDomain: true,
                contentType: "application/json; charset=utf-8",
                success: function(data){
                arrAllrecords[j]["cityName"] = data.list[0].city.name;
                arrAllrecords[j]["weather"] = data.list[0].weather[0].description;
                // call the callback here
                callback(arrAllrecords);
               } 
            });
           toDaysTimestamp = toDaysTimestamp - (24*60*60);
       }   
   }
}

并像这样使用它：

$(document ).ready(function() {
  var cityArray = new Array();
  cityArray[0] = "pune";
   getWeatherDataForCities(cityArray, function(arrAllrecords) {
       // Do something with your data
   });
});