Nodejs：闭包函数

//-------------optfile.js-------------------------
var fs = require('fs');
module.exports = {
	readfileSync: function (path) { //同步读取
		var data = fs.readFileSync(path, 'utf-8');
		console.log(data);
		console.log("同步方法执行完毕");
		return data;
	},
	readfile1: function (path, res) { //异步执行
		fs.readFile(path, function (err, data) {
			if (err) {
				console.log(err);
			} else {
				console.log(data.toString());
				res.write(data);//报错
			}
		});
		console.log("异步方法执行完毕");
	},
	readfile2: function (path, recall) { //异步执行
		fs.readFile(path, function (err, data) {
			if (err) {
				console.log("异步执行error：" + err);
				recall("文件不存在，异步执行error：" + err);
			} else {
				console.log(data.toString());
				recall(data);
			}
		});
		console.log("===异步方法执行完毕===");
	},
}

//-----------n5_readfile----读取文件---------------------
/*
 * 单线程异步
 */
var http = require('http');
var optfile = require('./model/optfile1.js');
http.createServer(function (request, response) {
	response.writeHead(200, {
		'Content-Type': 'text/html;  charset=utf-8'
	});
	if (request.url !== "/favicon.ico") { //清除第2此访问
		console.log('访问');
		function recall(data) {//闭包函数、回调函数
			console.log(data.toString());
			response.write(data);
			response.end(""); //不写则没有htpp协议尾
		}
		//optfile.readfile1('./view/01.txt', response);
		//response.end("ok");
		optfile.readfile2('./view/01.txt', recall);
		console.log("===主程序执行完毕===！");
	}
}).listen(8000);
console.log('Server  running  at  http://127.0.0.1:8000/');