nodejs学习之events的使用

var mysql = require("mysql");
var Event = require("events").EventEmitter;

var user = "lubingjie";
var pass = "123456";

var db = mysql.createConnection({host:"localhost",user:"root",password:"",database:"test"});//链接数据库
var ev = new Event();//实例化events

ev.on("error",function(err){//添加监听err的事件  统一的错误处理函数
    console.log("数据库出错了！");
});

function query(sql,fn){//执行函数
    db.query(sql,function(err,data){
        if(err)
            ev.emit("err",err);//执行监听的事件
        else{
            fn(data);
        }
    });
}

query("select * from user where username=‘"+user+"‘ and pass=‘"+pass+"‘",function(data){
    if(data.length==0){
        query("insert into user values(‘"+user+"‘,‘"+pass+"‘)",function(data){
            console.log("完成！");
        });
    }else{
        console.log("用户名已经存在！");
    }
});