https://github.com/bitcoinjs/bip21
var bip21 = require('bip21')
var decoded = bip21.decode('bitcoin:xxx?amount=20.3&label=Foobar')
console.log(decoded)
console.log(bip21.encode('xxx'))
console.log(bip21.encode('xxx', {
amount: 20.3,
label: 'Foobar'
}))