Javascript这指向Window对象 [英] Javascript this points to Window object

问题描述

我有以下代码。我希望在我的firebug控制台上看到archive对象，但是我看到了Window对象。这是正常的吗？

I have the following code. I expected to see "archive" object on my firebug console, but I see Window object. Is it normal?

var archive = function(){}

archive.prototype.action = {
    test: function(callback){
        callback();
    },
    test2: function(){
        console.log(this);
    }
}

var oArchive = new archive();
oArchive.action.test(oArchive.action.test2);

推荐答案

oArchive.action.test2 获取对 callback 然后指向的函数的引用，但是然后使用 callback（）调用该函数，这意味着它不作为方法调用，因此此是全局对象。关键点是这个没有绑定到函数：它取决于函数的调用方式。

oArchive.action.test2 gets you a reference to a function that callback then points to, but that function is then called using callback(), which means it is not called as a method and hence this is the global object. The key point is that this is not bound to a function: it's determined by how the function is called.

在这种情况下，您可以通过使用回调函数的调用此指向操作对象（但不是归档对象） c>或 apply 方法：

In this case you could explicitly make this point to the action object (but not the archive object) by using the callback function's call or apply method:

test: function(callback) {
    callback.call(this);
},

要获得此成为归档对象，你需要传递归档对象：

To get it this to be the archive object instead, you'll need to pass the archive object in:

var archive = function(){}

archive.prototype.action = {
    test: function(callback, archive){
        callback.call(archive);
    },
    test2: function(){
        console.log(this);
    }
}

var oArchive = new archive();
oArchive.action.test(oArchive.action.test2, oArchive);

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