javascript “this”、“$this”和“$(this)”有什么区别？

What is the difference between “this”, “$this” and “$(this)”?

提问by oshirowanen

What is the difference between these three forms:

这三种形式有什么区别：

this
$this
$(this)

回答by Nick Craver

In typicalusage you'll usually see them like this (the $thisusage may vary):

在典型用法中，您通常会看到它们是这样的（$this用法可能会有所不同）：

• this- Refers to the DOM element in the handler you're currently on, but this may be another object entirely in other situations, but it's always the context.
• $this- Usually created by var $this = $(this)a cached version of the jQuery wrapped version for efficiency (or chain off $(this)to get the same in many cases).
• $(this)- The jQuery wrapped version of the element, so you have access to all its methods(the ones in $.fnspecifically).

• this- 指的是您当前所在的处理程序中的 DOM 元素，但这在其他情况下可能完全是另一个对象，但它始终是上下文。
• $this- 通常由var $this = $(this)jQuery 包装版本的缓存版本创建以提高效率（或$(this)在许多情况下链接以获得相同的效果）。
• $(this)- 元素的 jQuery 包装版本，因此您可以访问其所有方法（特别是那些方法$.fn）。

回答by Quentin

• thisis the object upon which a method was called
• $thisis a poorly named variable with no special meaning
• $(this)calls the poorly named function $with thisas its only argument

• this是调用方法的对象
• $this是一个命名不当的变量，没有特殊含义
• $(this)调用命名功能不佳$与this作为其唯一参数

回答by Alexey Lebedev

In jQuery event handler:

在 jQuery 事件处理程序中：

• this- is a DOM element you assigned the event handler to
• $(this)- is a jQuery object created from that element
• $this- typically, a variable holding the result of $(this)

• this- 是您将事件处理程序分配给的 DOM 元素
• $(this)- 是从该元素创建的 jQuery 对象
• $this- 通常，一个保存结果的变量 $(this)

More generally:

更普遍：

• thisinside a function refers to the object or primitive the function is called on. When a function is used as a constructor, it refers to the new object being constructed. Outside of any function thisrefers to the global object (windowin non-strict mode).

  You can find a good detailed explanation on MDN.

• $thisis a variable name. In JavaScript variable names can start with $. Some like to use it as a prefix for variables containing jQuery objects:

  var body = document.body;   // no prefix for a plain DOM object
  var $body = jQuery('body'); // prefix for the same object wrapped in jQuery
  var $this = $(this);
  

• $(this)is a function call, where $is a function name, and thisis its argument:

  var $ = alert;
  $(this); // [object Window]
  

  $doesn't have any special meaning per se. But jQuery defines the $()function as a shorthand for jQuery(). Depending on its arguments, this function can do many different things.

• 函数内部的this指的是调用该函数的对象或原语。当函数用作构造函数时，它指的是正在构造的新对象。任何函数之外的都是this指全局对象（window在非严格模式下）。

  你可以在 MDN 上找到一个很好的详细解释。

• $this是一个变量名。在 JavaScript 中，变量名可以以$. 有些人喜欢将它用作包含 jQuery 对象的变量的前缀：

  var body = document.body;   // no prefix for a plain DOM object
  var $body = jQuery('body'); // prefix for the same object wrapped in jQuery
  var $this = $(this);
  

• $(this)是一个函数调用，其中$是函数名，this是它的参数：

  var $ = alert;
  $(this); // [object Window]
  

  $本身没有任何特殊意义。但是 jQuery 将该$()函数定义为jQuery(). 根据它的参数，这个函数可以做很多不同的事情。

回答by Jez

In the context of jQuery, 'this' is the object upon which a method was called. '$this' is indeed a poorly named variable with no special meaning. '$(this)' passes 'this' to jQuery, which will return a jQuery object associated with whatever 'this' is, as long as 'this' is a DOM object.

在 jQuery 的上下文中，'this' 是调用方法的对象。'$this' 确实是一个命名不佳的变量，没有特殊含义。'$(this)' 将 'this' 传递给 jQuery，只要 'this' 是一个 DOM 对象，它就会返回一个与任何 'this' 相关联的 jQuery 对象。

回答by tKe

Your question would be better served with more context.

提供更多上下文会更好地解决您的问题。

However I assume you're asking about variables within the context of a callback on an element's event (clickfor example).

但是，我假设您是在元素事件的回调上下文中询问变量（click例如）。

• thisis the context of your handler (normally the DOM element, in the case of a DOM event handler)
• $thisis usually used to store the result of $(this)
• $(this)returns the jQuery object that wraps this- see the jQuery documentationfor more information.

• this是处理程序的上下文（通常是 DOM 元素，在 DOM 事件处理程序的情况下）
• $this通常用于存储结果 $(this)
• $(this)返回包装的 jQuery 对象this-有关更多信息，请参阅jQuery 文档。

回答by Luca Matteis

Expanding on what David said:

扩展大卫所说的话：

• $thisis usually used to have a copy of the thisobject in the current scope. For example with var $this = this;you can use the variable $thisanywhere in the current scope and always be able to reference that object that would otherwise change if simply referenced with this... I personally dislike the $thisnaming convention and prefer something like var parentScope

• $(this)is a function (var $ = function(){}) used by some frameworks like jQuery or PrototypeJs. The reason it is used is because $is very easy to type instead of someLongFunctionNameand because it is usually called manytimes in the code it's easier to have it be as short as possible

• $this通常用于this在当前范围内拥有对象的副本。例如，var $this = this;您可以$this在当前范围内的任何位置使用该变量，并且始终能够引用该对象，如果简单地引用this...我个人不喜欢$this命名约定，并且更喜欢类似的东西var parentScope

• $(this)是var $ = function(){}一些框架（如 jQuery 或 PrototypeJs）使用的函数 ( )。使用它的原因是因为$很容易输入的，而不是someLongFunctionName因为它通常被称为很多在更容易的代码时代有它是越短越好