JavaScript UUID Generation using RFC4122 v4 (Random)

uuid-v4.js

// UPDATE: shorter, non RFC compatible, but safe enough version
function guid() {
  const s4 = () => Math.floor((1 + Math.random()) * 0x10000).toString(16).substring(1);
  return s4() + s4() + '-' + s4() + '-' + s4() + '-' + s4() + '-' + s4() + s4() + s4();
}




// Based off https://github.com/kelektiv/node-uuid
function uuid_v4() {
  // Step 1: Random Numbers Generator
  // Math.random()-based (RNG) - It's fast, but is of unspecified quality.
  var rnds = new Array(16);
  for (var i = 0, r; i < 16; i++) {
    if ((i & 0x03) === 0) r = Math.random() * 0x100000000;
    rnds[i] = r >>> ((i & 0x03) << 3) & 0xff;
  }

  // Step 2: Per 4.4, set bits for version and `clock_seq_hi_and_reserved`
  rnds[6] = (rnds[6] & 0x0f) | 0x40;
  rnds[8] = (rnds[8] & 0x3f) | 0x80;

  // Step 3: Convert bytes into a UUID string
  var bth = [];
  for (var i = 0; i < 256; ++i) {
    bth[i] = (i + 0x100).toString(16).substr(1);
  }
  i = 0;
  return bth[rnds[i++]] + bth[rnds[i++]] +
          bth[rnds[i++]] + bth[rnds[i++]] + '-' +
          bth[rnds[i++]] + bth[rnds[i++]] + '-' +
          bth[rnds[i++]] + bth[rnds[i++]] + '-' +
          bth[rnds[i++]] + bth[rnds[i++]] + '-' +
          bth[rnds[i++]] + bth[rnds[i++]] +
          bth[rnds[i++]] + bth[rnds[i++]] +
          bth[rnds[i++]] + bth[rnds[i++]];
}

uuid-v4.min.js

function uuid_v4(){for(var r,n=new Array(16),t=0;t<16;t++)0==(3&t)&&(r=4294967296*Math.random()),n[t]=r>>>((3&t)<<3)&255;n[6]=15&n[6]|64,n[8]=63&n[8]|128;var a=[];for(t=0;t<256;++t)a[t]=(t+256).toString(16).substr(1);return t=0,a[n[t++]]+a[n[t++]]+a[n[t++]]+a[n[t++]]+"-"+a[n[t++]]+a[n[t++]]+"-"+a[n[t++]]+a[n[t++]]+"-"+a[n[t++]]+a[n[t++]]+"-"+a[n[t++]]+a[n[t++]]+a[n[t++]]+a[n[t++]]+a[n[t++]]+a[n[t++]]}