使用自调用匿名函数和$(文档).ready [英] Using Self Calling Anonymous Functions and $(document).ready
问题描述
我刚刚学会了自称匿名函数。我遇到的一些代码片段使用了自调用函数和$(document).ready。使用两者似乎多余或毫无意义。
是否存在使用
<$ p的情况$ p>
(function(){
$(document).ready();
})();
vs。
$(document).ready(function(){
(function(){})();
});
我认为您要么立即执行脚本,要么在DOM加载后执行。我不明白为什么你们两个都在一起使用。
谢谢。
第一个例子肯定有一个用例。如果您在同一页面上加载了其他JS库/脚本,则无法保证它们不会覆盖 $
变量。 (当你在同一页面上有Prototype和jQuery时,这很常见。)
因此,如果Prototype使用 $
,你需要在你想使用jQuery的时候使用 jQuery
。这可能会非常难看:
jQuery(function(){
jQuery('a','#content') ).bind('click',function(){
if(jQuery(this).attr('href')=='www.google.com')
{
alert( 此链接转到Google);
jQuery(this).addClass('clicked'));
}
});
})
请记住,我们不能使用 $
因为这是Prototype在全局范围内的一种方法。
但如果你把它包装在这个...
(函数($){
$(函数(){
//您的代码在这里
});
})(jQuery);
$
实际上会引用jQuery库里面还在外面指的是Prototype!这有助于整理您的代码:
(函数($){
$(函数{}($ b) $ b jQuery('a','#content')。bind('click',function(){
if(jQuery(this).attr('href')=='www.google.com' )
{
alert(此链接转到Google);
jQuery(this).addClass('clicked'));
}
});
));
})(jQuery);
这是jQuery扩展的常见模式,以确保它们始终添加到jQuery对象中,但是可以使用 $
编写,以保持代码整洁。
I just recently learned about self calling anonymous functions. Some snippets of code that I came across used the self calling function along with the $(document).ready. It seems redundant, or pointless, to use both.
Is there a case where you'd use
(function(){
$(document).ready();
})();
vs.
$(document).ready(function(){
(function(){})();
});
I figure that you'd either want the script to be executed right away or after the DOM loaded. I can't see why you'd use both together.
Thanks.
There's definitely a use case for the first example. If you have other JS libraries/scripts loaded on the same page, there's no guarantee that they aren't overwriting the $
variable. (This is very common when you have Prototype and jQuery on the same page).
So if Prototype is using $
, you would need to use jQuery
anytime you wanted to work with jQuery. This can get quite ugly:
jQuery(function(){
jQuery('a', '#content').bind('click', function(){
if(jQuery(this).attr('href') == 'www.google.com')
{
alert("This link goes to Google");
jQuery(this).addClass('clicked'));
}
});
})
Remember, we can't use $
because that is a method from Prototype in the global scope.
But if you wrapped it inside of this..
(function($){
$(function(){
// your code here
});
})(jQuery);
The $
would actually reference the jQuery library inside while still referring to Prototype on the outside! This can help tidy up your code:
(function($){
$(function{}(
jQuery('a', '#content').bind('click', function(){
if(jQuery(this).attr('href') == 'www.google.com')
{
alert("This link goes to Google");
jQuery(this).addClass('clicked'));
}
});
));
})(jQuery);
This is a common pattern with jQuery extensions to ensure that they are always added to the jQuery object, but can be written using $
to keep the code tidy.
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