“this”，“$ this”和“$（this）”之间有什么区别？

What is the difference between these three forms:

这三种形式有什么区别：

this
$this
$(this)

6 个解决方案

#1

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

在典型的使用中，你通常会看到它们（这个用量可能会有所不同）：

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 - 指您当前处理的处理程序中的DOM元素，但这可能是完全在其他情况下的另一个对象，但它始终是上下文。
$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 - 通常由var $ this = $（this）创建jQuery包装版本的缓存版本以提高效率（或链接$（this）以在许多情况下获得相同的效果）。
$(this) - The jQuery wrapped version of the element, so you have access to all its methods (the ones in $.fn specifically).
$（this） - jQuery包装的元素版本，因此您可以访问其所有方法（特别是$ .fn中的方法）。

#2

this is the object upon which a method was called
这是调用方法的对象
$this is a poorly named variable with no special meaning
$这是一个命名不佳的变量，没有特殊含义
$(this) calls the poorly named function $ with this as its only argument
$（this）使用this作为唯一参数调用命名不佳的函数$

#3

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 - 是您为其分配事件处理程序的DOM元素
$(this) - is a jQuery object created from that element
$（this） - 是从该元素创建的jQuery对象
$this - typically, a variable holding the result of $(this)
$ this - 通常是一个保存$（this）结果的变量

More generally:

更普遍：

this inside 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 this refers to the global object (window in non-strict mode).

函数内部的this是指调用函数的对象或原语。当函数用作构造函数时，它引用正在构造的新对象。在任何函数之外，这指的是全局对象（非严格模式下的窗口）。

You can find a good detailed explanation on MDN.

您可以在MDN上找到详细的详细说明。
$this is a variable name. In JavaScript variable names can start with $. Some like to use it as a prefix for variables containing jQuery objects:

$ this是变量名。在JavaScript中，变量名称可以以$开头。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) is a function call, where $ is a function name, and this is its argument:

$（this）是一个函数调用，其中$是函数名，这是它的参数：
```
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.

$本身没有任何特殊含义。但是jQuery将$（）函数定义为jQuery（）的简写。根据其参数，此函数可以执行许多不同的操作。

#4

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，它就会返回与'this'相关的jQuery对象。

#5

Your question would be better served with more context.

您可以通过更多背景更好地解决问题。

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

但是我假设您在元素事件的回调上下文中询问变量（例如，单击）。

this is the context of your handler (normally the DOM element, in the case of a DOM event handler)
这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 is usually used to store the result of $(this)
$ this通常用于存储$（this）的结果
$(this) returns the jQuery object that wraps this - see the jQuery documentation for more information.
$（this）返回包装它的jQuery对象 - 有关更多信息，请参阅jQuery文档。

#6

Expanding on what David said:

扩展大卫所说的话：

$this is usually used to have a copy of the this object in the current scope. For example with var $this = this; you can use the variable $this anywhere 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 $this naming convention and prefer something like var parentScope

$ this通常用于在当前范围内拥有此对象的副本。例如，var $ this = this;你可以在当前范围内的任何地方使用变量$ this，并且总是能够引用那个如果简单地用这个引用会改变的对象......我个人不喜欢$ this命名约定并喜欢像var parentScope这样的东西
$(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 someLongFunctionName and because it is usually called many times in the code it's easier to have it be as short as possible

$（this）是一些函数（var $ = function（）{}），用于某些框架，如jQuery或PrototypeJs。使用它的原因是因为$很容易键入而不是someLongFunctionName，并且因为它通常在代码中多次调用，所以它更容易让它尽可能短

#1