JS implementation generates a random key of specified length

js The implementation generates a random specified length key

function generateKey(keyLength = 18) {
    
  let rlt = ''
  for (let i = 0; i < keyLength; i++) {
    
    if (Math.round(Math.random())) {
    
      rlt += Math.ceil(Math.random() * 9)
    } else {
    
      const ranNum = Math.ceil(Math.random() * 23)
      if (Math.round(Math.random())) {
    
        rlt += String.fromCharCode(65 + ranNum)
      } else {
    
        rlt += String.fromCharCode(97 + ranNum)
      }
    }
    // add -, What you don't want can be removed 
    if ((i + 1) % 6 === 0 && i > 2 && i < 17) {
    
      rlt += '-'
    }
  }
  return rlt
}

key It consists of an array and upper and lower case letters , Intermediate use - Division

const a = generateKey(16) // 91Sw86-t1P3UI-B6Sx
const b = generateKey() // b4TGq1-42Se7m-49d233
const c = generateKey(20) // n44Ix5-VIU8r5-J7b8I5E2