How do I send data to a node script from a browser?

Question

On page load, I am running this javascript in a script tag:

var xhttp = new XMLHttpRequest();
xhttp.open("POST", "http://lvh.me:1337", true);
xhttp.setRequestHeader('Content-Type', 'application/json; charset=UTF-8');
xhttp.send(JSON.stringify({hello:"goodbye"}));

Then the code for the node script is

var http = require('http');
http.createServer(function (request, response) {
    response.writeHead(200, {
        'Content-Type': 'text/plain',
        "Access-Control-Allow-Origin": "*",
        "Access-Control-Allow-Headers": "Origin, X-Requested-With, Content-Type, Accept"
    });
    console.log(request);
    response.end("");
}).listen(1337);

But in the console.log, I don't see my {"hello":"goodbye"} object anywhere. How do I get access to this object?

The request object is a stream, so I think you'll need to handle the data event. — MinusFour
– MinusFour, Commented Jan 22, 2016 at 17:06

T.J. Crowder · Accepted Answer · 2016-01-22 17:21:50Z

5

The createServer docs tell us that the callback you provide will be triggered by the request event. The request event docs tell us that request (the first argument) is an http.IncomingMessage. This does not have a body property, but it implements ReadableStream and you can listen for the 'data' event to gather the data:

// ES2015 (all of the below is supported in current NodeJS)
let body = '';
request.on('data', chunk => body += chunk);
request.on('end', () => console.log(JSON.parse(body)));

or

// ES5
var body = '';
request.on('data', function (chunk) {
   body += chunk;
});
request.on('end', function(){
  console.log(JSON.parse(body));
});

There are a lot of http server implementations out there that will abstract this process for you and give you a request.body to work with. body-parser is a prime example and will even parse JSON for you.

edited Jan 22, 2016 at 17:21

T.J. Crowder

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answered Jan 22, 2016 at 17:09

Explosion Pills

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5 Comments

charliebrownie Over a year ago

You're totally right... the typical express body-parser...!

Nick Manning Over a year ago

Thanks a lot, you're definitely on to something. I'm still having trouble. Now I'm getting SyntaxError: Unexpected end of input. It goes away when I comment out console.log(JSON.parse(body));

Explosion Pills Over a year ago

@NickManning would appear that body does not have valid JSON. Try just console.log(body)

Nick Manning Over a year ago

@ExplosionPills---doing that outputs [object Object].

Nick Manning Over a year ago

Nevermind, sorry. I forgot that I had taken out JSON.stringify in my html file while I was trying to figure it out. Thanks @ExplosionPills and TJ Crowder.

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