回调函数的返回值 [英] Return value from callback function

问题描述

我有几个函数调用另一个(浏览器中的集成函数)，如下所示:

I have few functions, which calls another (integrated functions in browser), something like this:

function getItems () {
    var xhr = new XMLHttpRequest();
    xhr.open("GET", "http://another.server.tld/", true);
    xhr.onreadystatechange = function() {
        if (xhr.readyState == 4) {
            items = $("a[href^=/courses/]", xhr.responseText);
        }
    };
    xhr.send();
}

因为我不想在里面写更多的代码，把每个逻辑功能分开，我需要这个函数来返回变量项.

As I don't want to write more code inside and make each logical functionality separated, I need this function to return variable items.

我知道可能会发生一些意外(网络/服务器不可用，响应时间长...)并且该函数可以在从服务器获取数据或发生超时后返回任何内容.

I know there can happen some accidents (network/server is not available, has long-response...) and the function can return anything after gets data from the server or timeout occurs.

推荐答案

这似乎是一个异步请求.我认为您无法从此函数返回数据.

This seems be an async request. I don't think you will be able to return data from this function.

相反，您可以将回调函数作为该函数的参数，并在收到响应时调用该回调.

Instead, you can take a callback function as an argument to this function and call that callback when you have the response back.

function getItems (callback) {
    var xhr = new XMLHttpRequest();
    xhr.open("GET", "http://another.server.tld/", true);
    xhr.onreadystatechange = function() {
        if (xhr.readyState == 4) {
            callback(xhr.responseText);
        }
    };
    xhr.send();
}

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