Cannot write data from POST to response

Question

Why cant send given POST data as response? When write response.write('Data is: ', data.toString()); i expect see data from post in browser, but its not work, why? if i use response.write('Some string'); not in callback request.on('data',...) i see written data in browser. If i use console.log(data) in callback request.on('data',...) i see data in console. But response not given any data in that callback. Why?

var server = require('http').createServer().listen(8080);
var template = '<form action="" method="post"><input placeholder="login" type="text" name="login" /><br><input type="password" placeholder="password" name="password" /><br><input type="submit" /></form>';

server.on('request', function(request, response){
    response.writeHead(200,{
        'Content-Type': 'text/html;charset=utf-8'
    });

    request.on('data', function(data){
        //console.log(data.toString());//it`s work, i see data in console
        response.write('Data is: '+ data.toString()); //but that code is not working. that data not append to response
    });

    response.write(template);
    response.end();
});

signature of `response.write` is `response.write(chunk[, encoding][, callback])` so you are providing `data.toString()` as 2nd argument instead of concatenating the string. — Ejaz, May 02 '15 at 20:16
you are ending the server response before the request's data event fires. you need to wait for `request.on("end")` and call `response.end();` from inside that. — dandavis, May 02 '15 at 20:28
possible duplicate of [Why is my variable unaltered after I modify it inside of a function? - Asynchronous code reference](http://stackoverflow.com/questions/23667086/why-is-my-variable-unaltered-after-i-modify-it-inside-of-a-function-asynchron) — Aaron Dufour, May 02 '15 at 22:18

NIPE-SYSTEMS · Answer 1 · 2015-05-03T07:47:33.710

Fix for your problem

var server = require('http').createServer().listen(8080);
var template = '<form action="" method="post"><input placeholder="login" type="text" name="login" /><br><input type="password" placeholder="password" name="password" /><br><input type="submit" /></form>';

server.on('request', function(request, response){
    var postData = '';

    response.writeHead(200,{
        'Content-Type': 'text/html;charset=utf-8'
    });

    request.on('data', function(data){
        postData += data.toString(); // store everything sent with the POST request
    });

    request.on('close', function(){
        response.write(template); // print out the template
        if(postData != '')
            response.write('Data is: ', postData); // if POST data was sent output the data
        response.end(); // close the connection
    });
});`

Explanation

Your problem is that node.js/javascript is an event-driven language based on callbacks. When a new request comes in everything in your request-event-function will be executed. This means that the following will be executed:

response.writeHead which simply predefines the status etc.
definition of a callback for the data-event of request. This means that whenever some POST data gets into the connection the callback will be executed.
But then: You write your template to the client and then you close the connection. By that every further callback of the data-event of request will write your POST data to a closed connection.

As the result nothing will be displayed at your website.

Thanks for answer but your code is brake browser and page is not loaded. And you print template only if method is post, but i wanna show template on every request type — Undisputed Shadow, May 02 '15 at 20:47
this will also return a response on the first data event, which is not always the only data event, which is why you need to wait on "end". — dandavis, May 02 '15 at 20:56

score 0 · Answer 2 · answered May 02 '15 at 20:29

var server = require('http').createServer().listen(8080);
var template = '<form action="" method="post"><input placeholder="login" type="text" name="login" /><br><input type="password" placeholder="password" name="password" /><br><input type="submit" /></form>';

server.on('request', function(request, response){
    response.writeHead(200,{
        'Content-Type': 'text/html;charset=utf-8'
    });

    request.on('data', function(data){
        response.write('OK');//thats not as response part
        console.log(123);//see that in console
    });

    response.write(template);
    response.end();
});

Please explain what you changed and why. Code-only answers are of limited value. — Gert Arnold, May 02 '15 at 21:53

score 0 · Answer 3 · answered May 02 '15 at 21:06

0

Thansk for all. I solved my problem. That code works for me

var server = require('http').createServer().listen(8080);
var template = '<form action="" method="post"><input placeholder="login" type="text" name="login" /><br><input type="password" placeholder="password" name="password" /><br><input type="submit" /></form>';

server.on('request', function(request, response){
    response.writeHead(200,{
        'Content-Type': 'text/html;charset=utf-8'
    });

    request.on('data', function(data){
        response.write(data.toString());
    });

    response.write(template);
    request.on('end', function(){
        response.end();
    });
});

answered May 02 '15 at 21:06

Undisputed Shadow

61
8

2

Please explain what you changed and why. Code-only answers are of limited value. – Gert Arnold May 02 '15 at 21:53
Sure. Problem was in that: in this case node.js executing asynchronously and he not wait executing callback for event "data". So node.js simply end request before callback for on('data') executed. I just provide request.on('end') and finish response in this event. As i known callbacks for that event executed only after all request-related operations is done – Undisputed Shadow May 03 '15 at 07:39

Cannot write data from POST to response

3 Answers3

Fix for your problem

Explanation