id generator with while

gistfile1.js

function a(size = 21) {
  let urlAlphabet = "sys_abcdefghijklmnopqrstuvwxyz0123456789";
  const length = urlAlphabet.length;
  let id = "";
  // A compact alternative for `for (var i = 0; i < step; i++)`.
  let i = size;
  while (i--) {
    // `| 0` is more compact and faster than `Math.floor()`.
    id += urlAlphabet[(Math.random() * length) | 0];
  }
  return id;
};

a(210);
/*
'xrsvkqe8r95py7zggvu4wtybow0eob4r222k9ysz2_5sms4sw_mw0my5wbyugm78sorrx1sd_hxyrzf8lusjk9v887mar_ai17u9vpmq55l_sgwf7bao6osdhttsrhuys25yegsh4rxmf2jln0um_dpmhudi8e7brtqarp8wkrdq6v26o23upso0uq72w11g9snt9e6fcngmem5nzp'
*/