Javascript jQuery.proxy() 用法
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jQuery.proxy() usage
提问by Reigel
I was reading the api about jQuery.proxy(). It looks promising but I was wondering in what situation is this best use. Can anyone enlighten me?
我正在阅读有关jQuery.proxy(). 它看起来很有希望，但我想知道在什么情况下最好使用。任何人都可以启发我吗？
回答by Anurag
When you want a function that has the thisvalue bound to a specific object. For example, in callbacks such as event handlers, AJAX callbacks, timeouts, intervals, custom objects, etc.
当您想要一个将this值绑定到特定对象的函数时。例如，在事件处理程序、AJAX 回调、超时、间隔、自定义对象等回调中。
This is just a manufactured example of a situation where it might be useful. Assuming there is a Personobject which has a property name. It is also linked to a text input element, and whenever the input value changes, the name in this person object gets updated too.
这只是一个可能有用的情况的制造示例。假设有一个Person具有属性名称的对象。它还链接到文本输入元素，并且每当输入值更改时，此人对象中的名称也会更新。
function Person(el) {
this.name = '';
$(el).change(function(event) {
// Want to update this.name of the Person object,
// but can't because this here refers to the element
// that triggered the change event.
});
}
One solution that we often use is to store the this context in a variable and use that inside the callback function such as:
我们经常使用的一种解决方案是将 this 上下文存储在一个变量中并在回调函数中使用它，例如：
function Person(el) {
this.name = '';
var self = this; // store reference to this
$(el).change(function(event) {
self.name = this.value; // captures self in a closure
});
}
Alternatively, we could have used jQuery.proxyhere so the reference to thisrefers to the object of Person instead of the element that triggered the event.
或者，我们也可以在jQuery.proxy这里使用，因此引用this指向 Person 的对象，而不是触发事件的元素。
function Person(el) {
this.name = '';
$(el).change(jQuery.proxy(function(event) {
this.name = event.target.value;
}, this));
}
Note that this feature has been standardized into ECMAScript 5 which now includes the bindmethod borrowed from prototypejsand is already available on some browsers.
请注意，此功能已标准化到 ECMAScript 5 中，它现在包括bind从prototypejs借用的方法，并且已经在某些浏览器上可用。
function Person(el) {
this.name = '';
$(el).change(function(event) {
this.name = event.target.value;
}.bind(this)); // we're binding the function to the object of person
}
回答by Nick Craver
It's just a shorthand method of setting the context for a closure, for example:
这只是设置闭包上下文的一种速记方法，例如：
$(".myClass").click(function() {
setTimeout(function() {
alert(this); //window
}, 1000);
});
However often we want thisto remain the same as the method we were in, which $.proxy()is used for, like this:
然而，我们经常希望this保持与我们$.proxy()使用的方法相同，它用于，如下所示：
$("button").click(function() {
setTimeout($.proxy(function() {
alert(this); //button
}, this), 1000);
});?
It's usually used for delayed calls, or anywhere you don't want to do a longhand method of declaring a closure. The string method of pointing the context to an object...well I haven't come across a practical use in every day code yet, but I'm sure there are applications, just depends what your object/event structure is.
它通常用于延迟调用，或者任何你不想做声明闭包的普通方法的地方。将上下文指向对象的字符串方法......好吧，我还没有在日常代码中遇到实际用途，但我确信有应用程序，只是取决于您的对象/事件结构是什么。
回答by Felix Kling
For example if you want to create callbacks. Instead of:
例如，如果您想创建回调。代替：
var that = this;
$('button').click(function() {
that.someMethod();
});
you can do:
你可以做：
$('button').click($.proxy(this.someMethod, this));
Or if you create a plugin that accepts callbacks and you have to set a specific context for the callback.
或者，如果您创建了一个接受回调的插件，并且您必须为回调设置特定的上下文。
