$ sudo npm install qr.js
$ sudo npm install -g qr.js

If want to update the qr.js package execute the command as below,

$ sudo npm update qr.js

Update package globally,

$ npm install -g qr.js

Git clone:

$ sudo  git clone https://github.com/rektide/qr.js.git

$ sudo  npm install -g ./qr.js

qr.js@0.0.0 /usr/lib/node_modules/qr.js

How to remove qr.js package :

You can uninstall or remove this package from your node_modules run the command as below,

$ sudo npm uninstall qr.js

Basic Information of qr.js NPM Package: