Simple UUID(v4) Generator

uuidv4.js

function uuidv4_1() {
  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'
    .split('')
    .map((c) => {
      if (c === 'x') return Math.floor(Math.random() * 0xf).toString(16); // [0-9a-f]
      if (c === 'y') return Math.floor(Math.random() * 4 + 8).toString(16); // [89ab]
      return c;
    })
    .join('');
}

function uuidv4_2() {
  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'
    .replace(/x/g, () => Math.floor(Math.random() * 0xf).toString(16))
    .replace('y', Math.floor(Math.random() * 4 + 8).toString(16));
}
// faster
function uuidv4_3() {
  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'
    .split('')
    .reduce((c, i) => c + (
      i === 'x' ? Math.floor(Math.random() * 0xf).toString(16)
      : i === 'y' ? Math.floor(Math.random() * 4 + 8).toString(16)
      : i), '')
}
function uuidv4_4() {
  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'
    .replace(/(x)|(y)|([-4])/g, function(match, p1, p2, p3) {
      if (p1) return Math.floor(Math.random() * 0xf).toString(16);
      if (p2) return Math.floor(Math.random() * 4 + 8).toString(16);
      return p3;
    });
}

// oneliner(uuidv4_1)
[...'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'].map((c)=>c==='x'?Math.floor(Math.random()*0xf).toString(16):c==='y'?Math.floor(Math.random()*4+8).toString(16):c).join('');

// oneliner(uuidv4_2)
'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/x/g,()=>Math.floor(Math.random() * 0xf).toString(16)).replace('y',Math.floor(Math.random()*4+8).toString(16));