node-qr is a simple NodeJS binding to the libqrencode C library written by Kentaro Fukuchi (http://fukuchi.org/works/qrencode/index.en.html).

To use node-qr, you will first need to install the libqrencode C library

For Mac OS X (assumed MacPorts installed)

port install qrencode

For Ubuntu Linux

apt-get install qrencode

Others (see instructions on site)

http://fukuchi.org/works/qrencode/index.en.html

Node-qr is available in the Node Package Manager (NPM)

npm install qr

Currently node-qr only comes with an encoder. The usage is simple

encoder.encode(value, path = null, options = {});

First, require the module

var Encoder = require('qr').Encoder;
var encoder = new Encoder;

The following example will encode a given value and emit an 'end' event with PNG data upon completion

// add an event listener for the 'end' event
// which fires upon encoding completion
encoder.on('end', function(png_data){
    // png_data is an instance of Buffer
    // do something
});
encoder.encode('some value');

Alternatively, you can pass a file path for the PNG data to be saved to

encoder.on('end', function(){
    // if you specify a file path, nothing will be passed to the end listener
    // do something
});
encoder.encode('some value', '/tmp/my_qr_file.png');

If at any time an error occurs, an 'error' event will be emitted

encoder.on('error', function(err){
    // err is an instance of Error
    // do something
});

See the tests in test/qr.js for more ways to use the encoder.

While node-qr and libqrencode can encode images up to 4000 characters, this library makes no attempt to automatically set error correction and version options based on the size of the value (yet, anyway). You are responsible for determining what length your values will be and adjusting the options accordingly.

See 2D QR Code Barcode Generation Guide for more information on limitations of QR Codes and the devices that read them.

The following options can be passed via the third argument of the encode method, which should be an object

• dot_size: specify the size of dot (pixel). (default=3)
• margin: specify the width of margin. (default=4)
• level: specify error correction level from L (lowest) to H (highest). (default=L)
• case_sensitive: ignore case distinctions and use only upper-case characters. (default=true)
• version: specify the version of the symbol. (default=1)

For more information around options, see the docs provided for the libqrencoder library here

Feedback and pull requests are always welcomed. This is a work-in-progress. Any help is greatly appreciated.