Node.js从fs.readFileSync（）到fs.readFile（）

问题描述

在一个请求处理程序中，同步（同步）我使用的版本，其工作原理如下：

  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


2. 我理解readFile是异步的，因此理论上我应该等待
   整个文件在渲染之前读取，所以我应该引入
   addListener？我可能会混淆不同的事情。

编辑：我试图重构代码如下：

  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，我想是因为它应该等待所有数据已经被读取，在resp.write（data）之前，我该如何发出信号？

解决方案

  var fs = requires（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 （）; 
}）; 
} 
  

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

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

Edit: 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();
    }

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

解决方案

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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