Combine N arrays into unique combinations

createUniqueCombinationsFromArrays.js

const createUniqueCombinationsFromArrays = (head, ...tail) =>
tail.length 
  ? head.reduce((a, x) => [...a, ...createUniqueCombinationsFromArrays(...tail).map(_=>x+_)],[]) 
  : head

const a1 = ['1','2','3','4']
const a2 = ['a','b']
const a3 = ['x','y']
const a4 = [':',',','?','!', '&'] 

const unique1And2 = createUniqueCombinationsFromArrays(a1, a2)
console.log(unique1And2)
console.log(unique1And2.length)
const unique1And2And3 = createUniqueCombinationsFromArrays(a1, a2, a3)
console.log(unique1And2And3)
console.log(unique1And2And3.length)
const unique1And2And3And4 = createUniqueCombinationsFromArrays(a1, a2, a3, a4)
console.log(unique1And2And3And4)
// 4 * 2 * 2 * 5 = 80
console.log(unique1And2And3And4.length)

createUniqueCombinationsOfObjectsFromArrays.js

const createUniqueCombinationsOfObjectsFromArrays = (head, ...tail) =>
tail.length 
  ? head.reduce((a, x) => [...a, ...createUniqueCombinationsOfObjectsFromArrays(...tail).map(_=>({...x, ..._}))],[]) 
  : head

const  users = [ 
  {user_name:'user1'},
  {user_name:'user2'},
]

const  audiences = [ 
  {audience_name:'audience1'},
  {audience_name:'audience2'},
]

const  creatives = [ 
  {creative_name:'creative1'},
  {creative_name:'creative2'},
]

console.log(createUniqueCombinationsOfObjectsFromArrays(users, audiences,creatives))
console.log(createUniqueCombinationsOfObjectsFromArrays(users, audiences,creatives).length)