Iterate on many arrays simultaneously

forEachOnArrays.js

const forEach = (as, cb) => {
  // necessary tests:
  //   - as is an array and all items in as are arrays
  //   - length of all arrays in as are the same
  as[0].forEach( (serie, i) => cb( as.map( serie => serie[i] ), i, as) )
}

// ---------------- testing

const A = [1, 2, 3, 4]
const B = [5, 6, 7, 8]

forEach([A, B], ([a, b]) => {
    console.log(a, b)
})

/* result
1 5
2 6
3 7
4 8
*/