Splitting arrays into X elements and “the rest”

// takes an array and the number of elements to extract from the start
const spliceHead = (array, sizeOfHead) => {
  // create a copy, because `.splice()` changes the array in place
  const copy = [...array]

  // cut the first `sizeOfHead` elements from the array and store them
  const head = copy.splice(0, sizeOfHead)

  // return TWO arrays: the first `sizeOfHead` elements and “the rest”
  return [head, copy]
}

// this can split an array into “the first three, and everything else”
spliceHead(['John', 'Paul', 'George', 'Ringo'], 3)
// ⇒ [ ['John', 'Paul', 'George'], ['Ringo'] ]

// we can assign the results to two variables with destructuring
const [head, rest] = spliceHead(['Bibidi', 'Babidi', 'Boo'], 2)
console.log(`${head[0]}, ${head[1]}, and ${rest.length} more`)
// ⇒ 'Bibidi, Babidi, and 1 more'