NODEJS 中使用二维码 qr-image
https://www.npmjs.com/package/qr-image
npm install qr-image
var qr = require('qr-image');
var code = qr.image("yourcodehere", {type: 'png'});
res.setHeader('Content-type', 'image/png'); //sent qr image to client side
code.pipe(res);