My question is about handling methods using Node.JS, ajax and mysql with the code below.
If the client enters the correct password and username, the server returns "true" value to my front-end (index.html) and the page redirects to chat.html page if username and password correct returns "false" and a message shown.
However, when I try with the same code and user info, sometimes I got "Error: write after end" and sometimes I don't and chat.html appears. I suppose it is related to async programming since I use "response.write" a lot, it seems that they are mixed with the ones in fs.readFile() method.
How should I replace my codes or how can I overcome this situation? Since I am a new learner of node.js it is pretty confusing for me.
var http = require ('http');
var url = require('url');
var fs = require('fs');
var json;
var mysql = require('mysql');
var con = mysql.createConnection({
host: "127.0.0.1",
user: "root",
password: "123456",
database: "web-chat",
timeout:"100ms"
});
con.connect(function (err) {
if (err){
throw err;
}
http.createServer(function (request,response) {
var q = url.parse(request.url, true);
var filename = "."+q.pathname;
var uid = q.query.uid;
var pass = q.query.pass;
console.log(filename);
if (q.pathname == "/" || q.pathname == "" || q.pathname=="./") {
filename = "./index.html";
}
if (q.pathname == "/login"){
console.log("id: "+uid," pass:"+pass);
con.query("SELECT * FROM user_table WHERE user_id='"+uid+"' AND password='"+pass+"'", function (err, result, fields) {
if (err) throw err;
//console.log(result[0].user_id);
console.log(uid);
if(result==""){ //LOGIN FAILED
response.write("false");
return response.end();
}
else { //LOGIN SUCCESSFUL
response.write("true");
return response.end();
}
});
}
fs.readFile(filename, function (err, data) {
if(err){
console.log("false");
response.writeHead(404,{'Content-Type':'text/html'});
return response.end();
}else{
console.log("true");
response.writeHead(200,{'Content-Type':'text/html'});
response.write(data);
return response.end();
}
});
}).listen(1337);
});<!DOCTYPE html>
<html lang="en">
<head>
<style>
#frame-div{
border: lightgray solid 1px;
border-radius: 3px;
width: 40%;
margin: auto;
}
body{
font-family: Calibri;
}
.label{
display: table-cell;
padding-top: 15px;
padding-bottom: 5px;
}
.table{
display: table;
}
.table-row{
display: table-row;
}
</style>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<div id="frame-div" class="table">
<div class="table-row">
<div class="label">Kullanıcı Adı:</div>
<div class="label"><input id="user-id" type="text"></div>
</div>
<div class="table-row">
<div class="label">Parola:</div>
<div class="label"><input id="password" type="password"></div>
</div>
<div class="table-row">
<div class="label">
<input type="button" value="Giriş Yap" onclick="Login()">
<form action="registration.html" style="display: inline-block">
<input type="submit" value="Üye Ol">
</form></div>
</div>
</div>
<p id="content"></p>
<script>
function Login() {
var userId=document.getElementById("user-id").value;
var password=document.getElementById("password").value;
var xhttp;
xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function () {
if(this.readyState == 4 && this.status == 200){
var isregisteredUser=this.responseText;
console.log("reg user:"+isregisteredUser);
//console.log(this.responseText.uid);
if(isregisteredUser=='true'){
window.location.href='chat.html?uid='+userId;
}else
{
document.getElementById("content").innerHTML += "<br/>"+"Hatalı Kullanıcı Adı/Parola";
}
}
};
xhttp.open("GET","login?uid="+userId+"&pass="+password,true);
xhttp.send();
}
</script>
</body>
</html>Error code that I got sometimes and sometimes I don't with the same code:
events.js:183
throw er; // Unhandled 'error' event
^
Error: write after end
at write_ (_http_outgoing.js:622:15)
at ServerResponse.write (_http_outgoing.js:617:10)
at Query.<anonymous> (C:\Node JS Projects\Web Chat App\server.js:53:30)
at Query.<anonymous> (C:\Node JS Projects\Web Chat App\node_modules\mysql\lib\Connection.js:502:10)
at Query._callback (C:\Node JS Projects\Web Chat App\node_modules\mysql\lib\Connection.js:468:16)
at Query.Sequence.end (C:\Node JS Projects\Web Chat App\node_modules\mysql\lib\protocol\sequences\Sequence.js:83:24)
at Query._handleFinalResultPacket (C:\Node JS Projects\Web Chat App\node_modules\mysql\lib\protocol\sequences\Query.js:139:8)
at Query.EofPacket (C:\Node JS Projects\Web Chat App\node_modules\mysql\lib\protocol\sequences\Query.js:123:8)
at Protocol._parsePacket (C:\Node JS Projects\Web Chat App\node_modules\mysql\lib\protocol\Protocol.js:278:23)
at Parser.write (C:\Node JS Projects\Web Chat App\node_modules\mysql\lib\protocol\Parser.js:76:12)
