在 JavaScript 中创建自定义回调 [英] Create a custom callback in JavaScript

问题描述

我需要做的就是在当前函数执行结束时执行一个回调函数.

All I need to do is to execute a callback function when my current function execution ends.

function LoadData() 
{
    alert('The data has been loaded');
    //Call my callback with parameters. For example,
    //callback(loadedData , currentObject);
}

这个函数的消费者应该是这样的:

A consumer for this function should be like this:

object.LoadData(success);

function success(loadedData , currentObject) 
{
  //Todo: some action here 
}

我该如何实施?

推荐答案

实际上，您的代码几乎可以按原样工作，只需将您的回调声明为参数，您就可以使用参数名称直接调用它.

Actually, your code will pretty much work as is, just declare your callback as an argument and you can call it directly using the argument name.

function doSomething(callback) {
    // ...

    // Call the callback
    callback('stuff', 'goes', 'here');
}

function foo(a, b, c) {
    // I'm the callback
    alert(a + " " + b + " " + c);
}

doSomething(foo);

那会调用doSomething，它会调用foo，它会提醒东西到这里了".

That will call doSomething, which will call foo, which will alert "stuff goes here".

注意传递函数引用(foo)非常重要，而不是调用函数并传递其结果(foo())>).在您的问题中，您做得对，但值得指出，因为这是一个常见错误.

Note that it's very important to pass the function reference (foo), rather than calling the function and passing its result (foo()). In your question, you do it properly, but it's just worth pointing out because it's a common error.

有时您想调用回调，以便它看到this 的特定值.您可以使用 JavaScript call 函数轻松做到这一点:

Sometimes you want to call the callback so it sees a specific value for this. You can easily do that with the JavaScript call function:

function Thing(name) {
    this.name = name;
}
Thing.prototype.doSomething = function(callback) {
    // Call our callback, but using our own instance as the context
    callback.call(this);
}

function foo() {
    alert(this.name);
}

var t = new Thing('Joe');
t.doSomething(foo);  // Alerts "Joe" via `foo`

你也可以传递参数:

function Thing(name) {
    this.name = name;
}
Thing.prototype.doSomething = function(callback, salutation) {
    // Call our callback, but using our own instance as the context
    callback.call(this, salutation);
}

function foo(salutation) {
    alert(salutation + " " + this.name);
}

var t = new Thing('Joe');
t.doSomething(foo, 'Hi');  // Alerts "Hi Joe" via `foo`

有时以数组的形式传递你想要给回调的参数很有用，而不是单独传递.您可以使用 apply 来做到这一点:

Sometimes it's useful to pass the arguments you want to give the callback as an array, rather than individually. You can use apply to do that:

function Thing(name) {
    this.name = name;
}
Thing.prototype.doSomething = function(callback) {
    // Call our callback, but using our own instance as the context
    callback.apply(this, ['Hi', 3, 2, 1]);
}

function foo(salutation, three, two, one) {
    alert(salutation + " " + this.name + " - " + three + " " + two + " " + one);
}

var t = new Thing('Joe');
t.doSomething(foo);  // Alerts "Hi Joe - 3 2 1" via `foo`

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