function getCode (size = 6, part = '') {
  let str = '' + Math.random()
  str = str.replace(/^0\.?/, '')
  part = part + str
  return part.length < size 
    ? getCode(size, part) 
    : part.slice(0, size)
}

for (let i = 0; i < 10; i++) {
  console.log(getCode())
}