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

我正在尝试了解 Node.js 中的同步与异步，尤其是读取 HTML 文件.

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，我使用的同步版本如下所示:

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在理论上是异步的，所以我应该在渲染它之前等待整个文件被读取，所以我应该引入一个addListener吗?我可能会混淆不同的东西.

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.

我尝试像这样重构代码:

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.我猜是因为它应该在 resp.write(data) 之前等待所有数据被读取，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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