javascript - '杂耍异步' - 为什么我的解决方案根本不返回任何内容？

Question

在针对 learnyounode 中的“Async Juggling”作业要求我做的事情提出问题并获得非常有帮助的答案后，我开始自己实现它。

问题是，我的设置没有成功!尽管我已经提到了其他解决方案，但当我执行 learnyounode verify myscript.js 时，我的设置根本没有返回任何结果。

GIST: jugglingAsync.js

var http = require('http');

var app = (function () {
    // Private variables...
    var responsesRemaining,
        urls = [],
        responses = [];

   var displayResponses = function() {
        for(var iterator in responses) {
            console.log(responses[iterator]);
        }
    };

    // Public scope...
    var pub = {};

    pub.main = function (args) {
        responsesRemaining = args.length - 2;

        // For every argument, push a URL and prep a response.
        for(var i = 2; i < args.length; i++) {
            urls.push(args[i]);
            responses.push('');
        }

        // For every URL, set off an async request.
        for(var iterator in urls) {
            var i = iterator;
            var url = urls[i];

            http.get(url, function(response) {
                response.setEncoding('utf8');

                response.on('data', function(data) {
                    if(response.headers.host == url)
                        responses[i] += data;
                });

                response.on('end', function() {
                    if(--responsesRemaining == 0)
                        displayResponses();
                });
            });
        }
    };

    return pub;
})();

app.main(process.argv);

问题:我做错了什么？

Answer 1

这一行

    for(var iterator in urls) {

并没有按照您的想法行事。它实际上遍历 urls 的属性(参见 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...in )。相反，你必须做类似的事情

    for(var i = 0; i < urls.length; i++) {
        var url = urls[i];
        ...
    }

或

    urls.forEach(function(url, index) {
        ...
    });