SOURCE

const arr = [['A','B'],['a','b'],[1,2]]

function descales (args) {
  return args.reduce((result, curArr) => {
    const newResult = []
    result.forEach((resultItem) => {
      curArr.forEach((item) => {
        newResult.push(resultItem.concat([item]))
      })
    })
    console.log(newResult)
    return newResult
  },[[]]).map((arg) => arg.join(''))
  
}

descales(arr)