blocks|key|1508299|text|创建一个匿名函数closure和all，而final+()告诉它自己执行。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1508300|其基本相同于：|1508301|function+name+(){...}
name();|code-block|syntax|javascript|1508302|因此，这段代码基本上没有什么特别之处，它只是创建一个方法并调用它的“捷径”，而不需要命名它。|1508303|这也意味着该函数是一次性的，或者是对象上的内部函数，当你需要闭包的特性时，它是最有用的。|1508304|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

The creates an anonymous function, closure and all, and the final () tells it to execute itself.

It is basically the same as:

<pre><code>function name (){...}
name();
</code></pre>

So basically there is nothing special about this code, it just a 'shortcut' to creating a method and invoking it without having to name it. 

This also implies that the function is a one off, or an internal function on an object, and is most useful when you need to the features of a closure.

blocks|key|1508356|text|这是一个自动执行的匿名函数。末尾的()实际上是调用函数。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1508357|有一本好书(我已经读过)解释了Javascript中这些类型的语法的一些用法，那就是Object+Oriented+Javascript。|offset|length|1508358|entityMap|0|LINK|mutability|MUTABLE|url|https://rads.stackoverflow.com/amzn/click/com/1847194141^0|0|16|Q|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

That is a self executing anonymous function. The () at the end is actually calling the function.

A good book (I have read) that explains some usages of these types of syntax in Javascript is <a href="https://rads.stackoverflow.com/amzn/click/com/1847194141" rel="nofollow noreferrer" rel="nofollow noreferrer">Object Oriented Javascript</a>.

blocks|key|1508412|text|第一组括号中的内容计算为一个函数。然后，第二组括号执行此函数。所以如果你有一些东西想要在加载时自动运行，这就是你让它加载和执行的方式。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1508413|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

The stuff in the first set of brackets evaluates to a function. The second set of brackets then execute this function. So if you have something that want to run automagically onload, this how you'd cause it to load and execute.

blocks|key|1508476|text|这是一个被调用的匿名函数。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1508477|这样做的目的是创建一个新的作用域，使局部变量不会从该作用域中溢出。例如：|1508478|var+test+=+1;
(function()+{
++var+test+=+2;
})();
test+==+1+//+true|code-block|syntax|javascript|1508479|关于此语法的一个重要注意事项是，您应该养成使用分号结束语句的习惯，如果您还没有这样做的话。这是因为当您调用Javascript时，它允许在函数名和它的括号之间换行。|1508480|下面的代码片段将导致错误：|1508481|var+aVariable+=+1
var+myVariable+=+aVariable

(function()+{/*...*/})()|1508482|这是它实际做的事情：|1508483|var+aVariable+=+1;
var+myVariable+=+aVariable(function()+{/*...*/})
myVariable();|1508484|创建新块作用域的另一种方法是使用以下语法：|1508485|new+function()+{/*...*/}|1508486|不同之处在于，前一种技术不会影响关键字"this“所指向的位置，而第二种技术会影响。|1508487|Javascript+1.8也有一个let语句，可以完成同样的任务，但不用说，大多数浏览器都不支持它。|1508488|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|13|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|14|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|15|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|16|8|@]|9|@]|A|$]]|$1|M|3|N|5|F|7|17|8|@]|9|@]|A|$G|H]]|$1|O|3|P|5|6|7|18|8|@]|9|@]|A|$]]|$1|Q|3|R|5|F|7|19|8|@]|9|@]|A|$G|H]]|$1|S|3|T|5|6|7|1A|8|@]|9|@]|A|$]]|$1|U|3|V|5|F|7|1B|8|@]|9|@]|A|$G|H]]|$1|W|3|X|5|6|7|1C|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|6|7|1D|8|@]|9|@]|A|$]]|$1|10|3|-4|5|6|7|1E|8|@]|9|@]|A|$]]]|11|$]]

It's an anonymous function being called.

The purpose of that is to create a new scope from which local variables don't bleed out. For example:

<pre><code>var test = 1;
(function() {
 var test = 2;
})();
test == 1 // true
</code></pre>

One important note about this syntax is that you should get into the habit of terminating statements with a semi-colon, if you don't already. This is because Javascript allows line feeds between a function name and its parentheses when you call it.

The snippet below will cause an error:

<pre><code>var aVariable = 1
var myVariable = aVariable

(function() {/*...*/})()
</code></pre>

Here's what it's actually doing:

<pre><code>var aVariable = 1;
var myVariable = aVariable(function() {/*...*/})
myVariable();
</code></pre>

Another way of creating a new block scope is to use the following syntax:

<pre><code>new function() {/*...*/}
</code></pre>

The difference is that the former technique does not affect where the keyword "this" points to, whereas the second does.

Javascript 1.8 also has a let statement that accomplishes the same thing, but needless to say, it's not supported by most browsers.

blocks|key|1508504|text|John+Resig+explains+self-executing+anonymous+functions+here。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1508505|entityMap|0|LINK|mutability|MUTABLE|url|http://books.google.co.uk/books?id=GgJN2CC_2s4C&pg=PA29&lpg=PA29&dq=John%2Bresig%2Bself%2Bexecuting%2Banonymous%2Bfunction&source=web&ots=7w-ceWchMH&sig=oLWUghev2PlbhBU0DXyw2i8fzM8&hl=en&sa=X&oi=book_result&resnum=1&ct=result#v=onepage&q&f=false^0|0|1N|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

<a href="http://books.google.co.uk/books?id=GgJN2CC_2s4C&amp;pg=PA29&amp;lpg=PA29&amp;dq=John+resig+self+executing+anonymous+function&amp;source=web&amp;ots=7w-ceWchMH&amp;sig=oLWUghev2PlbhBU0DXyw2i8fzM8&amp;hl=en&amp;sa=X&amp;oi=book_result&amp;resnum=1&amp;ct=result#v=onepage&amp;q&amp;f=false" rel="nofollow noreferrer">John Resig explains self-executing anonymous functions here</a>.

blocks|key|1723682|text|另请参阅Douglas+Crockford的优秀"JavaScript:+The+Good+Parts“，可在这里从O‘’Reilly获得：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1723683|http://oreilly.com/catalog/9780596517748/|offset|length|1723684|..。在YUIblog的视频中，这里：|1723685|http://yuiblog.com/blog/2007/06/08/video-crockford-goodstuff/|1723686|entityMap|0|LINK|mutability|MUTABLE|url|1^0|0|0|15|0|0|0|0|1P|1|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@]|9|@$D|T|E|U|1|V]]|A|$]]|$1|F|3|G|5|6|7|W|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|X|8|@]|9|@$D|Y|E|Z|1|10]]|A|$]]|$1|J|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|K|$L|$5|M|N|O|A|$P|C]]|Q|$5|M|N|O|A|$P|I]]]]

See also Douglas Crockford's excellent "JavaScript: The Good Parts," available from O'Reilly, here:

<a href="http://oreilly.com/catalog/9780596517748/" rel="nofollow noreferrer"><a href="http://oreilly.com/catalog/9780596517748/" rel="nofollow noreferrer">http://oreilly.com/catalog/9780596517748/</a></a>

... and on video at the YUIblog, here:

<a href="http://yuiblog.com/blog/2007/06/08/video-crockford-goodstuff/" rel="nofollow noreferrer"><a href="http://yuiblog.com/blog/2007/06/08/video-crockford-goodstuff/" rel="nofollow noreferrer">http://yuiblog.com/blog/2007/06/08/video-crockford-goodstuff/</a></a>

<pre><code>(function() 
 {
 //codehere
 }
)();
</code></pre>

What is special about this kind of syntax?
What does ()(); imply?

How do you explain this structure in JavaScript?

(function()  {     //codehere })();这种语法有什么特别之处？()()；意味着什么？

问如何在JavaScript中解释这种结构？
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问如何在JavaScript中解释这种结构？EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问如何在JavaScript中解释这种结构？
EN