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, Jan 22 '16 at 17:06

score 5 · Accepted Answer · edited Jan 22 '16 at 17:21

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 '16 at 17:21

T.J. Crowder

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answered Jan 22 '16 at 17:09

Explosion Pills

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You're totally right... the typical express `body-parser`...! – charliebrownie Jan 22 '16 at 17:20
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));` – Nick Manning Jan 22 '16 at 17:35
1

@NickManning would appear that `body` does not have valid JSON. Try just `console.log(body)` – Explosion Pills Jan 22 '16 at 17:42
@ExplosionPills---doing that outputs `[object Object]`. – Nick Manning Jan 22 '16 at 17:45
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. – Nick Manning Jan 22 '16 at 17:50

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

1 Answers1