Javascript 试图理解'；这'；内部Prorotype和Lambda函数

所以今天我编写了一个AJAX对象

我创建了一个构造函数ajaxObj：

    function ajaxObj( arg1, arg2, wrapper ) {
             this.form = arg1;
             this.btn  = arg2;
             this.msg  = "Update successful";

             this.url  = "process.php";
             this.wrap = wrapper; // this is the div the callback uses

             this.serial = null; // serialized form for POSTing

             this.callback = function () {
                  var div = document.createElement("div");
                  div.innerHTML = this.msg;
                  div.setAttribute( "id", "desiredID" );
                  this.wrap.appendChild(div);

             }

             this.btn.onclick = initXHR;
    }

在给定页面上实例化了多个ajaxObj类型的对象。我想包括那些不会改变并且应该在原型上共享的功能：

ajaxObj.prototype = {
     constructor: ajaxObj,

     makeXHR: function () { 
               // cross browser XHR code returns XHR obj
     }

     makeSer: function () {
            this.serial = $(this.form).serialize();
     }

     initXHR: function () {
            // this is where shit gets weird!
            this.makeSer(); // makeSer function doesnt exit

            var http = this.makeXHR(); // makeXHR doesn't exist

            http.onreadystatechange = function () {
                     /* this function checked for 
                        http.status / http.readyState
                        and attempted to call this.callback() 
                        which of course didn't exist.

                        I also tried to change instance
                        properties here which did not work */
            }

            http.open( "POST", this.url, true ); /* this.url did not work
                                                     and had to be replaced
                                                     with "process.php"    */
            http.setRequestHeaders("Content-Type","application/x..."); // TL;DT
            http.send( this.serial ) // <--- this works just fine???
     }

与

。。。。请不要让我困惑。我的印象是我已经弄明白了。当我使用var关键字时，在构造函数中设置this=this似乎不起作用，而且很明显（javascript中的情况并不总是那么明显）删除了var关键字集，该关键字集等于用最近的对象实例实例化的值。

请看一看。可能您调用的函数“错误”，即不在

ajaxObj

实例上。给我们看一下那个调用

---

this.serial

起作用而

this.url

不起作用的原因是您刚刚明确地分配给了

this.serial

，尽管它可能不是您期望的对象的属性。

只要浏览一下您的代码，我就可以看到只有在单击目标按钮时才会调用initXHR函数开火。如果您在initXHR中检查此，我相信您会发现它是您的按钮

我认为基于你目前的课堂设计，你需要使用旧的

var self = this;

在构造函数中，并将initXHR设置为特权函数（在构造函数中），以便访问它。我对下面的代码进行了注释，以向您展示我添加到您的ctor中的内容

function ajaxObj( arg1, arg2, wrapper ) {

     // Assign this -> self at the start of the func
     var self = this;

     this.form = arg1;
     this.btn  = arg2;
     this.msg  = "Update successful";

     this.url  = "process.php";
     this.wrap = wrapper;

     this.serial = null;

     this.callback = function () {
          var div = document.createElement("div");
          div.innerHTML = this.msg;
          div.setAttribute( "id", "desiredID" );
          this.wrap.appendChild(div);

     }

     // Make initXHR a privileged function, ie. one that has
     // access to private variables in ctor
     this.initXHR = function () {

         self.url // should be accessible here
     }

     this.btn.onclick = this.initXHR; // Assign it.
}

---

您的右侧-而this.serial似乎不适用于页面上的所有表单（共有6个表单）。MDN是我的主页。我已经读了很多关于这个关键词的文章，并且进行了我自己的实验来尝试理解它，但我会再读一遍那个篇文章…谢谢，我确信我已经尝试过了。。。只是我把initXHR留在了原型中，而不是放在构造函数中。这正是我想做的。顺便说一句，完全脱离主题，我刚刚查看了Brendan Eich的网站，JavaScript的未来似乎有一些很酷的东西：）我很高兴这有帮助。我会对他的网站嗤之以鼻的，干杯。

var self = this;

function ajaxObj( arg1, arg2, wrapper ) {

     // Assign this -> self at the start of the func
     var self = this;

     this.form = arg1;
     this.btn  = arg2;
     this.msg  = "Update successful";

     this.url  = "process.php";
     this.wrap = wrapper;

     this.serial = null;

     this.callback = function () {
          var div = document.createElement("div");
          div.innerHTML = this.msg;
          div.setAttribute( "id", "desiredID" );
          this.wrap.appendChild(div);

     }

     // Make initXHR a privileged function, ie. one that has
     // access to private variables in ctor
     this.initXHR = function () {

         self.url // should be accessible here
     }

     this.btn.onclick = this.initXHR; // Assign it.
}