jquery 变量语法
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jquery variable syntax
提问by dnagirl
I'm learning jQuery by trying to understand other people's code. I ran into this:
我正在通过尝试理解其他人的代码来学习 jQuery。我遇到了这个：
jQuery.fn.myFunc = function(options, callback) {
//stuff
jQuery(this)[settings.event](function(e) {
var self = this,
$self = jQuery( this ),
$body = jQuery( "body" );
//etc.
}
//more stuff
}
My understanding is that $refers to the jQuery object. So why put $with $selfand $body? And is selfthe same as $self?
我的理解是$指的是 jQuery 对象。那么为什么要$加上$selfand$body呢？和self一样$self吗？
回答by David Hellsing
$selfhas little to do with $, which is an alias for jQuery in this case. Some people prefer to put a dollar sign together with the variable to make a distinction between regular vars and jQuery objects.
$self与$几乎没有关系，在这种情况下，它是 jQuery 的别名。有些人喜欢将美元符号与变量放在一起，以区分常规变量和 jQuery 对象。
example:
例子：
var self = 'some string';
var $self = 'another string';
These are declared as two different variables. It's like putting underscore before private variables.
它们被声明为两个不同的变量。这就像在私有变量之前放置下划线。
A somewhat popular pattern is:
一个有点流行的模式是：
var foo = 'some string';
var $foo = $('.foo');
That way, you know $foo is a cached jQuery object later on in the code.
这样，您就知道 $foo 是稍后在代码中缓存的 jQuery 对象。
回答by Quentin
This is pure JavaScript.
这是纯 JavaScript。
There is nothing special about $. It is just a character that may be used in variable names.
没有什么特别之处$。它只是一个可以在变量名中使用的字符。
var $ = 1;
var $$ = 2;
alert($ + $$);
jQuery just assigns it's core function to a variable called $. The code you have assigns thisto a local variable called selfand the results of calling jQuery with thisas an argument to a global variable called $self.
jQuery 只是将它的核心功能分配给一个名为$. 您分配this给一个局部变量的代码self和调用 jQuery 的结果this作为一个全局变量的参数$self。
It's ugly, dirty, confusing, but $, selfand $selfare all different variables that happen to have similar names.
它是丑陋的、肮脏的、令人困惑的，但是$，self并且$self都是碰巧具有相似名称的不同变量。
回答by BalusC
No, it certainly is not. It is just another variable name. The $()you're talking about is actually the jQuery core function. The $selfis just a variable. You can even rename it to fooif you want, this doesn't change things. The $(and _) are legal characters in a Javascript identifier.
不，当然不是。它只是另一个变量名。在$()你所谈论的实际上是jQuery的核心功能。该$self仅仅是一个变量。foo如果需要，您甚至可以将其重命名为，这不会改变事情。在$（和_）是一个JavaScript标识符合法字符。
Why this is done so is often just some code convention or to avoid clashes with reversed keywords. I often use it for $thisas follows:
为什么这样做通常只是一些代码约定或避免与反向关键字发生冲突。我经常使用它$this如下：
var $this = $(this);
回答by Rich
self and $self aren't the same. The former is the object pointed to by "this" and the latter a jQuery object whose "scope" is the object pointed to by "this". Similarly, $body isn't the body DOM element but the jQuery object whose scope is the body element.
self 和 $self 不一样。前者是“this”指向的对象，后者是一个jQuery对象，其“范围”是“this”指向的对象。类似地，$body 不是 body DOM 元素，而是其作用域是 body 元素的 jQuery 对象。
回答by Jan
The dollarsign as a prefix in the var name is a usage from the concept of the hungarian notation.
