如何将使用fs.readFileSync（）的Node.js代码重构为使用fs.readFile（）？ [英] How to refactor Node.js code that uses fs.readFileSync() into using fs.readFile()?

问题描述

我正在尝试在Node.js中同步还是异步，尤其是在读取HTML文件时。

I'm trying to get my head around synchronous versus asynchronous in Node.js, in particular for reading an HTML file.

在请求处理程序中，我所使用的同步版本m使用，其工作原理如下：

In a request handler, the synchronous version that I'm using, which works is the following:

    var fs = require("fs");
    var filename = "./index.html";
    var buf = fs.readFileSync(filename, "utf8");
    
    function start(resp) {
        resp.writeHead(200, { "Content-type": "text/html" });
        resp.write(buf);
        resp.end();
    }
    
    exports.start = start; 

1. 使用 readFile（）的版本是什么？


2. 我知道 readFile 是异步的，因此从理论上讲，我应该等待整个文件读取后再渲染它，所以我应该介绍一个 addListener 吗？我可能会混淆其他事情。

1. What would be the version using readFile()?
2. I understand that readFile is asynchronous so theoretically, I should wait for the entire file to be read before rendering it, so should I introduce an addListener? I might be confusing different things.

编辑：我试图重构如下代码：

I have tried to refactor the code like this:

    var fs = require("fs");
    var filename = "./index.html";
    function start (resp) {
        resp.writeHead(200, { "Content-Type": "text/html" });
        fs.readFile(filename, "utf8", function (err, data) {
            if (err) throw err;
            resp.write(data);
        });
        resp.end();
    }

我得到一个空白页。我猜是因为它应该等待所有数据被读取，然后在 resp.write（data）之前，我该如何发出信号？

I get a blank page. I guess it's because it should wait for all the data to be read, before resp.write(data), how do I signal this?

推荐答案

var fs = require("fs");
var filename = "./index.html";

function start(resp) {
    resp.writeHead(200, {
        "Content-Type": "text/html"
    });
    fs.readFile(filename, "utf8", function(err, data) {
        if (err) throw err;
        resp.write(data);
        resp.end();
    });
}

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