面向对象的javascript - “this”关键字和访问对象内的功能 [英] object oriented javascript - "this" key word and accessing functions within an object

问题描述

我是第一次尝试一些OO JS。这是我到目前为止所提出的：

I am, for the first time, trying some OO JS. Here is what I've come up with so far:

var myObj = {
1   site_url: window.location.protocol + "//" + window.location.hostname + "/",
2   site_host: window.location.hostname,
3   site_brand: this.readCookie('aCookieName'),
4   site_full_url: this.site_url + window.location.pathname,
5   /***
6   Read a cookie by its name;
7   **/
8
9   readCookie: function(name) {
10      var nameEQ = name + "=";
11      var ca = document.cookie.split(';');
12      for(var i=0;i < ca.length;i++) {
13          var c = ca[i];
14          while (c.charAt(0) == ' ') c = c.substring(1, c.length);
15          if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
16      }
17      return null;
18  },
19
20  /***
20  ***/
22  SaySomeThing: function() {
23      alert(this.site_brand);
24  }
}

跟我说话，我是新来的。我遇到的问题是：

Bear with me, I am new to this. The problem I have is:

第3行 - 我收到错误：readCookie未定义;

第4行 - 另一个错误：site_url是undefined;

Line # 3 - I get an error: readCookie is undefined;
Line # 4 - Another error: site_url is undefined;

请帮我解决上述问题。

推荐答案

In javascript，一个对象没有这个的概念。

In javascript, an object has no concept of this.

这个<的值/ code>关键字在函数中通过如何确定该函数被确定。

The value of the this keyword is determined in a function by how that function is called.

例如，在你的 myObj 中，如果你这样做：

For example, in your myObj, if you do:

myObj.readCookie('someName');

然后在 readCookie 函数内，此将设置为 myObj 。

Then inside the readCookie function, this will be set to myObj.

如果你想 site_brand 调用 readCookie 函数，然后你应该给 site_brand 它自己的函数调用它：

If you want site_brand to call the readCookie function, then you should give site_brand its own function that calls it:

site_brand: function() { return this.readCookie('aCookieName'); },

...并称之为：

myObj.site_brand()

...所以这个里面的 site_brand 函数是对 myObj 。

...so that this inside the site_brand function is a reference to myObj.

编辑：问题中的代码有所改变（由于格式化问题）认为）。

The code in the question changed a bit (due to formatting I think).

答案是一样的，但我只是注意到在中调用 this.site_brand 只要从 myObj SaySomeThing ， SaySomeThing 就可以了。 >。

The answer is the same, but I'd just note that calling this.site_brand in the SaySomeThing function is fine as long as SaySomeThing was called from myObj.

 // this is fine
SaySomeThing: function() {
   alert(this.site_brand);
}

 // as long as you're calling it something like
myObj.SaySomeThing();

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