uuid-ish.js

// Random quick uuidv4 implementation
// https://gist.github.com/jed/982883
const b = (
    a                  // placeholder
  ) => {
    return a           // if the placeholder was passed, return
      ? (              // a random number from 0 to 15
        a ^            // unless b is 8,
        Math.random()  // in which case
        * 16           // a random number from
        >> a/4         // 8 to 11
        ).toString(16) // in hexadecimal
      : (              // or otherwise a concatenated string:
        [1e7] +        // 10000000 +
        -1e3 +         // -1000 +
        -4e3 +         // -4000 +
        -8e3 +         // -80000000 +
        -1e11          // -100000000000,
        ).replace(     // replacing
          /[018]/g,    // zeroes, ones, and eights with
          b            // random hex digits
        )
  }


// Main logic

const uuid = b();
const suuid = uuid.replace(/-/g, '')

var result = ''

// JS version of PHP's "pack(h*)"
for (i = 0; i < suuid.length; i += 2) {
    let word = suuid[i]
    if (((i + 1) >= suuid.length) || typeof suuid[i + 1] === 'undefined') {
      word += '0'
    } else {
      word += suuid[i + 1]
    }

    // low nibble first
    word = word[1] + word[0]
    const char = String.fromCharCode(parseInt(word, 16))

    result += char
}

// URL-safe base64 representation
const compressed = Buffer.from(result, 'binary')
    .toString('base64')
    .replace(/[=\/\-\+]+/g, '')

console.log('original uuidv4', uuid, uuid.length, 'characters')
console.log('compressed uuidv4', compressed, compressed.length, 'characters')