前端生成uuid

function getUUid() {
  const s = [];
  const hexDigits = '0123456789abcdef';
  for (let i = 0; i < 36; i++) {
    s[i] = hexDigits.substr(Math.floor(Math.random() * 0x10), 1);
  }
  s[14] = '4';
  s[19] = hexDigits.substr((s[19] & 0x3) | 0x8, 1);
  s[8] = s[13] = s[18] = s[23] = '-'; 
  return s.join('');
}