index.js
function merge(prev, current, next) {
  return prev
    .concat()
    .reverse()
    .concat([current], next)
}
function merge(prev, current, next) {
  return prev
    .concat()
    .reverse()
    .concat([current], next)
}
function merge ( prev , current , next ) { return prev . concat ( ) . reverse ( ) . concat ( [ current ] , next ) }
Merge a previous array, with a current value, and a following array.
Merge a previous array with a current value and a following array .