异步同步读取文件内容对比

/**
 * Created by Administrator on 2016/8/3.
 */
var http = require("http");
//Node 导入文件系统模块
var fs = require("fs");
function start(req, res){
    res.writeHead(200, {"Content-Type": "text/plain"});
    res.write("异步读取文件和同步读取文件的对比！");
    res.end("over");
}
//创建一个http服务器，并监听端口号为3001，host为127.1.1.1
var server = http.createServer(start).listen("3001","127.1.1.1",function(){
    var port = server.address().port;
    var host = server.address().address;
    console.log("应用实例，访问地址为 http://%s:%s", host, port);
});
//异步读取[非阻塞]
console.log("异步开始：");
//异步读取文件内容的函数: readFile()
fs.readFile("index.txt", "utf-8", function(err, data){
    if(err){
        console.log(err);
    }else{
        console.log(data);
    }
});
console.log("end异步");
//同步读取[阻塞，阻塞之后代码的执行]
console.log("同步开始：");
//同步读取文件内容的函数: readFileSync()
var data = fs.readFileSync("index.txt", "utf-8");
console.log(data);
console.log("end同步");