load()函数如何允许用户提供回调? [英] How does the load() function allow the user to provide a callback?

问题描述

在javascript中，对于库/框架来说，让我们定义一个用于对数据进行后处理的回调函数非常流行.

In javascript it's very popular for libraries/frameworks to let us define a callback function for post-processing of data.

例如

load("5", function(element) {
    alert(element.name);
});

我想知道load()函数看起来如何能够让用户提供回调?

I wonder how the load() function looks like to be able to let the user provide a callback?

是否有很好的教程?

推荐答案

好吧， load 函数看起来像这样:

Well, the load function could look like this:

function load(arg, callback) {

  var element = { name: "foo " + arg }; // something to pass

  if (typeof callback == 'function') {
    callback(element);
  }
}

通过 typeof 检查，确保回调参数是我们可以调用的对象，即函数.

With the typeof check we make sure that the callback argument is an object that we can invoke, a function.

然后是您的示例:

load("5", function(element) {
    alert(element.name); // Will show `"foo 5"`.
});

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