JS: How to parse Payments URI Scheme

parsePaymentURIScheme.js

/**
 * Payments URI Scheme Parser
 * @param {String} - eg. "bitcoin:1XXX?amount=123&comment=%66%77"
 * @see also: https://github.com/bitcoin/bips/blob/master/bip-0021.mediawiki
 */
function parsePaymentURIScheme(s) {
  const tmp = s.match(/^(\w+)\:(\w+)\??(.+)?/);
  const protocol = (tmp && tmp.length >= 1) ? tmp[1] : null;
  const address = (tmp && tmp.length >= 2) ? tmp[2] : null;
  const qstr = (tmp && tmp.length >= 3) ? tmp[3] : null;
  const params = parseQS(qstr);
  if (!protocol || !address) return null;
  const ret = {};
  if (protocol) ret.protocol = protocol;
  if (address) ret.address = address;
  if (params) ret.params = params;
  return ret

  function parseQS(s) {
    if (!s) return null;
    const lines = s.split('&');
    if (!lines) return null;
    const arr = [];
    for (let len = lines.length, i = 0; i < len; i++) {
      const line = lines[i];
      const [k, v] = line.split('=');
      if (!k || !k.trim()) continue;
      arr.push({
        key: k,
        value: (v) ? decodeURIComponent(v) : null,
      });
    }
    return arr;
  }
};

//
// test
//

let ret = parsePaymentURIScheme("bitcoin:1XXXXX?amount=123&comment=%66%77");
console.log(JSON.stringify(ret, null, 2));
/*
{
  "protocol": "bitcoin",
  "address": "1XXXXX",
  "params": [
    {
      "key": "amount",
      "value": "123"
    },
    {
      "key": "comment",
      "value": "fw"
    }
  ]
}
*/

ret = parsePaymentURIScheme("bitcoin:1XXXXX");
console.log(JSON.stringify(ret, null, 2));
/*
{
  "protocol": "bitcoin",
  "address": "1XXXXX"
}
*/

ret = parsePaymentURIScheme("bitcoin");
console.log(JSON.stringify(ret, null, 2)); // null

ret = parsePaymentURIScheme(":1XXXX");
console.log(JSON.stringify(ret, null, 2)); // null

ret = parsePaymentURIScheme("");
console.log(JSON.stringify(ret, null, 2)); // null