Javascript CRC16校验

Javascript CRC16校验

function crc16(hexString) {
  let crc = 0x0000;
  const polynomial = 0x1021;
  let byte_val, bit, c15;
  for (let i = 0; i < hexString.length / 2; i++) {
    byte_val = parseInt(hexString.substr(i * 2, 2), 16);
    for (let k = 0; k < 8; k++) {
      bit = ((byte_val >> (7 - k) & 1) == 1);
      c15 = ((crc >> 15 & 1) == 1);
      crc <<= 1;
      if (c15 ^ bit) {
        crc ^= polynomial;
      }
    }
  }
  crc &= 0xffff;
  return ('0000' + crc.toString(16)).slice(-4);
}