blocks|key|521014|text|传递给函数的this设置执行的上下文，因此在匿名函数中，this引用window。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|521015|然后就可以编写this.alert('');了。|521016|entityMap^0|6|4|S|4|Y|6|0|7|F|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|I|$]]

<code>this</code> passed to the function sets the context of the execution, so inside your anonymous function <code>this</code> refers to the <code>window</code>.

You can than write <code>this.alert('');</code>.

blocks|key|737586|text|试试这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|737587|function+Foo()+{

++(function+()+{
++++console.log(this);
++++//+>+Foo
++}).call(this);

++(function+()+{
++++console.log(this);
++++//+>+undefined+in+strict+mode,+or+Window+in+non+strict+mode
++})();
}

var+bar+=+new+Foo;|code-block|syntax|javascript|737588|因此，如果您出于任何原因使用它，它是一种使IIFE表现得好像它是Foo的成员函数一样的方法，特别是在创建用户定义的对象类型的实例时。|offset|length|style|CODE|737589|entityMap|0|LINK|mutability|MUTABLE|url|http://benalman.com/news/2010/11/immediately-invoked-function-expression/^0|0|0|W|3|L|4|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@$I|X|J|Y|K|L]]|9|@$I|Z|J|10|1|11]]|A|$]]|$1|M|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

Try this:

<pre><code>function Foo() {

 (function () {
 console.log(this);
 // &gt; Foo
 }).call(this);

 (function () {
 console.log(this);
 // &gt; undefined in strict mode, or Window in non strict mode
 })();
}

var bar = new Foo;
</code></pre>

So, if for whatever reason you use this, it's a way to make the <a href="http://benalman.com/news/2010/11/immediately-invoked-function-expression/" rel="noreferrer">IIFE</a> act as if it were a member function of <code>Foo</code>, specifically when creating instances of a user-defined object type.

blocks|key|521120|text|我对此很好奇，因为我刚刚看过John+Resig关于this+video的演讲。Yoshi有一个很好的答案，但我必须在控制台日志中测试一下才能理解，我认为对他的答案的修改可能会帮助一些像我这样一开始遇到麻烦的人：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|521121|function+Foo()+{
++this.foo+=+true;
++(function+()+{
++++++console.log("Foo+=+"+%2B+this.foo);
++++++//+Outputs+undefined
++}());
++(function+()+{
++++++console.log("Foo+=+"+%2B+this.foo);
++++++//+Outputs+true
++}).call(this);

++(function+()+{
++++++console.log(this);
++++++//+Outputs+undefined+in+strict+mode,+or+Window+in+non+strict+mode
++++++//+Anonymous+functions+usually+default+to+the+global+scope
++})();
}

var+bar+=+new+Foo;|code-block|syntax|javascript|521122|对我来说，并排查看第一个和第二个更有意义，这表明.call(这)本质上提供了将当前上下文传递给匿名函数的能力。|521123|谢谢你的问题，也感谢Yoshi清晰的回答！|521124|entityMap|0|LINK|mutability|MUTABLE|url|http://www.youtube.com/watch?v=0LKDImgRfrg^0|Q|A|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@]|C|$]]|$1|K|3|L|5|6|7|10|8|@]|9|@]|C|$]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]]]

I was curious about this as well as I had just seen John Resig's talk about <a href="http://www.youtube.com/watch?v=0LKDImgRfrg">this video</a>. Yoshi had a great answer but I had to test it in a bit in console log to understand and I thought this modification to his answer might help some people who were having trouble at first like me:

<pre><code>function Foo() {
 this.foo = true;
 (function () {
 console.log("Foo = " + this.foo);
 // Outputs undefined
 }());
 (function () {
 console.log("Foo = " + this.foo);
 // Outputs true
 }).call(this);

 (function () {
 console.log(this);
 // Outputs undefined in strict mode, or Window in non strict mode
 // Anonymous functions usually default to the global scope
 })();
}

var bar = new Foo;
</code></pre>

It just made a little more sense to me to see the first and second ones side by side, showing that .call(this) essentially gives you the ability to pass the current context to an anonymous function.

Thanks for the question and thanks Yoshi for the clear answer!

I have seen JavaScript written like this (it was at a demonstration, and I don’t have the actual code at hand, but it was implied this was normal):

<pre><code>(function() { 

 var a = 1;

 this.sayA = function() {
 alert(a);
 }

}).call(this);

sayA();
</code></pre>

I suppose it is written an an anonymous function so that the variable <code>a</code> is not globally available.

What could the point of the <code>.call(this)</code> be? Since this function was not nested, <code>this</code> was just the window. How does it differ from just writing <code>()</code> at the end?

Why write ".call(this)" at the end of an javascript anonymous function?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我见过JavaScript是这样写的(它是在一个演示中，我手头没有实际的代码，但它暗示这是正常的)：(function() {        var a = 1;    this.sayA = function() {        alert(a);    }}).call(this);sayA();我认为它是一个匿...

问为什么要在javascript匿名函数的末尾写上".call(this)“？
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问为什么要在javascript匿名函数的末尾写上".call(this)“？
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