在jQuery中将对象传递给回调函数 [英] passing object to callback function in jquery

问题描述

我最近正在研究小型聊天模块，该模块需要不断检查服务器中是否有新消息.

I am recently working on small chat module , which require continuously checking the server for new message.

我正在向服务器发送ajax请求，并且服务器保持连接状态，直到找到新消息为止(长时间轮询).

I am sending a ajax request to a server , and the server hold's the connection until new message is found(long polling).

代码:

var chatController = function(){

//other variable declaration

/**
*  Ajax call to monitor the new message , on complete of ajax call sending other call
*/

this.checkNewMessage = function(){
  console.log(this); // placed this for debugging purpose
       $.ajax({
         url : SITEURL.CHECK_MESSAGE,
         data : this.currrentUserDetails,
         dataType : 'json' ,
         cache    : false,
         success  :(function(obj){
            //temp = obj;
            return obj.parseNewMessageResponse;
         })(this),
         complete: (function(obj){
            //temp = obj;
            return obj.checkNewMessage;
         })(this),  
       });


};

  // other function and variable

});

当我尝试致电

var mainController = new chatController();
mainController.checkNewMessage();

问题

我以为我可以向服务器发送连续的单个请求，但是令我惊讶的是，我只能一个接一个地发送2个a​​jax请求.

What i thought was that i would be able to send continuous single request to server, but to my surprise I only could send 2 ajax request one after the other.

我的调试

当我尝试调试时，我发现传递的第一个调用this对象指向chatController

When i tried to debug , i traced out that for the first call this object being passed points to the chatController

         complete: (function(obj){
            return obj.checkNewMessage;
         })(this),     // this here point to chatController object

第二次传递的this对象指向ajax object

For the second time this object being passed points to the ajax object

         complete: (function(obj){
            return obj.checkNewMessage;
         })(this),     // this here point to ajax object

我正在使用JavaScript闭包将chatController对象传递给jquery的complete参数

I am using JavaScript closure to pass the chatController object to complete parameter of jquery

所以我想要的是将参数传递给jQuery complete函数的方法，以便它指向我的原始引用

So what i want is way to pass parameter to jQuery complete function so that it's point to my original reference

推荐答案

有各种可能的> $.proxy :

我认为是最佳做法.

There are various posible cross-browser solutions

You can use $.proxy:

In my opinion, the best practice.

$.ajax({
    //...
    success: $.proxy(function(json) {
         // `this` refers to the second argument of `$.proxy`
    }, this)
});

您可以设置 context选项:

$.ajax({
    //...
    context: this,
    success: function(json) {
         // `this` refers to the value of `context`
    }
});

或使用关闭:

var self = this;
$.ajax({
    //...
    success: function(json) {
         // `this` refers to ajax request, use self instead
         $(self).dosomething();
    }
});

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