SG PayNow QR Code Generator Sample

paynow.js

String.prototype.padLeft = function (n, str) {
  if (n < String(this).length) {
    return this.toString();
  }
  else {
    return Array(n - String(this).length + 1).join(str || '0') + this;
  }
}

function crc16(s) {
  var crcTable = [0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5,
    0x60c6, 0x70e7, 0x8108, 0x9129, 0xa14a, 0xb16b,
    0xc18c, 0xd1ad, 0xe1ce, 0xf1ef, 0x1231, 0x0210,
    0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
    0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c,
    0xf3ff, 0xe3de, 0x2462, 0x3443, 0x0420, 0x1401,
    0x64e6, 0x74c7, 0x44a4, 0x5485, 0xa56a, 0xb54b,
    0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
    0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6,
    0x5695, 0x46b4, 0xb75b, 0xa77a, 0x9719, 0x8738,
    0xf7df, 0xe7fe, 0xd79d, 0xc7bc, 0x48c4, 0x58e5,
    0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
    0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969,
    0xa90a, 0xb92b, 0x5af5, 0x4ad4, 0x7ab7, 0x6a96,
    0x1a71, 0x0a50, 0x3a33, 0x2a12, 0xdbfd, 0xcbdc,
    0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
    0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03,
    0x0c60, 0x1c41, 0xedae, 0xfd8f, 0xcdec, 0xddcd,
    0xad2a, 0xbd0b, 0x8d68, 0x9d49, 0x7e97, 0x6eb6,
    0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
    0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a,
    0x9f59, 0x8f78, 0x9188, 0x81a9, 0xb1ca, 0xa1eb,
    0xd10c, 0xc12d, 0xf14e, 0xe16f, 0x1080, 0x00a1,
    0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
    0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c,
    0xe37f, 0xf35e, 0x02b1, 0x1290, 0x22f3, 0x32d2,
    0x4235, 0x5214, 0x6277, 0x7256, 0xb5ea, 0xa5cb,
    0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
    0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447,
    0x5424, 0x4405, 0xa7db, 0xb7fa, 0x8799, 0x97b8,
    0xe75f, 0xf77e, 0xc71d, 0xd73c, 0x26d3, 0x36f2,
    0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
    0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9,
    0xb98a, 0xa9ab, 0x5844, 0x4865, 0x7806, 0x6827,
    0x18c0, 0x08e1, 0x3882, 0x28a3, 0xcb7d, 0xdb5c,
    0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
    0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0,
    0x2ab3, 0x3a92, 0xfd2e, 0xed0f, 0xdd6c, 0xcd4d,
    0xbdaa, 0xad8b, 0x9de8, 0x8dc9, 0x7c26, 0x6c07,
    0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
    0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba,
    0x8fd9, 0x9ff8, 0x6e17, 0x7e36, 0x4e55, 0x5e74,
    0x2e93, 0x3eb2, 0x0ed1, 0x1ef0];

  var crc = 0xFFFF;
  var j, i;

  for (i = 0; i < s.length; i++) {

    c = s.charCodeAt(i);
    if (c > 255) {
      throw new RangeError();
    }
    j = (c ^ (crc >> 8)) & 0xFF;
    crc = crcTable[j] ^ (crc << 8);
  }

  return ((crc ^ 0) & 0xFFFF).toString(16).toUpperCase().padStart(4, '0');
}


function generatePayNowStr( opts ) {

  const p = [
    { id: '00', value: '01' },                    // ID 00: Payload Format Indicator (Fixed to '01')
    { id: '01', value: '12' },                    // ID 01: Point of Initiation Method 11: static, 12: dynamic
    {
      id: '26', value:                            // ID 26: Merchant Account Info Template
        [{ id: '00', value: 'SG.PAYNOW' },
        { id: '01', value: '2' },                 // 0 for mobile, 2 for UEN. 1 is not used.
        { id: '02', value: opts.uen },            // PayNow UEN (Company Unique Entity Number)
        { id: '03', value: opts.editable.toString() },       // 1 = Payment amount is editable, 0 = Not Editable
        { id: '04', value: opts.expiry }]         // Expiry date (YYYYMMDD)
    },
    { id: '52', value: '0000' },                  // ID 52: Merchant Category Code (not used)
    { id: '53', value: '702' },                   // ID 53: Currency. SGD is 702
    { id: '54', value: opts.amount.toString() },  // ID 54: Transaction Amount
    { id: '58', value: 'SG' },                    // ID 58: 2-letter Country Code (SG)
    { id: '59', value: 'COMPANY NAME' },          // ID 59: Company Name
    { id: '60', value: 'Singapore' },             // ID 60: Merchant City
    {
      id: '62', value: [{                         // ID 62: Additional data fields
        id: '01', value: opts.refNumber           // ID 01: Bill Number
      }]
    }
  ]

  let str = p.reduce((final, current) => {
    if (Array.isArray(current.value)) { //nest loop
      current.value = current.value.reduce((f, c) => {
        f += c.id + c.value.length.toString().padLeft(2) + c.value;
        return f
      }, "")
    }
    final += current.id + current.value.length.toString().padLeft(2) + current.value;
    return final
  }, "")

  // Here we add "6304" to the previous string
  // ID 63 (Checksum) 04 (4 characters)
  // Do a CRC16 of the whole string including the "6304"
  // then append it to the end.
  str += '6304' + crc16(str + '6304');

  return str;

}

May I know can we limit a qr code for one transaction only? For example, once a user has scanned the QR code and paid, the QR code is expired and doesn't allow transaction anymore.

May I know can we limit a qr code for one transaction only? For example, once a user has scanned the QR code and paid, the QR code is expired and doesn't allow transaction anymore.

You need bank transaction API access for that.. The QR code has no way to know if it was even scanned at all... :)

I see, thank you for the answer.