Nodejs Web服务器在页面加载时两次调用requestListener [英] Nodejs web server calling requestListener twice when page is loaded

问题描述

以下是文档中的示例Web服务器，带有添加的计数器.每当客户端/浏览器请求页面时，它将计数器打印到控制台.

The following is the example web server from the documentation, with an added counter. It prints the counter to the console whenever a client/browser requests the page.

但是，浏览器要求两次调用它.为什么?

However, it's being called twice when requested by the browser. Why?

这是我期望发生的事情:

This is what I would expect would happen:

browser : Hello World 1
console : Counter 1
[reload page]
browser : Hello World 2
console : Counter 2

但这会发生:

browser : Hello World 1
console : Counter 1
          Counter 2
[reload page]
browser : Hello World 3
console : Counter 3
          Counter 4

我使用命令行运行代码

$ node example.js

这是代码:

  var 
    http = require('http'),
    counter = 0,
    sys = require('util');
  http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    counter++;
    res.end('Hello World ' + counter + '\n');
    sys.puts('Counter ' + counter);
  }).listen(8000, "");

推荐答案

在编程中，遇到困难时，跟踪代码以更好地了解正在发生的情况总是很方便的.最简单的方法是放入更多的debug/print语句，直到您看到正在发生的事情为止.

In programming, when stuck, it's always handy to trace the code to better understand what's happening. The easiest way to do this is to put more debug/print statements in till you can see what's going on.

将sys.puts行更改为:

Change the sys.puts line to:

sys.puts('Counter ' + counter + " from " + req.url);

我想您会发现第二个请求是浏览器请求该网站的网站图标.

I think you'll find that the 2nd request is the browser requesting the favicon for the site.

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