ffff001.js

function getLargestArray(a, b) {
  let as = a.map(_ => 'x').join('');
  let bs = b.map(_ => 'x').join('');
  let arx = new RegExp(as);
  let brx = new RegExp(bs);
  let aNotShorter = as.match(brx) !== null;
  let bNotShorter = bs.match(arx) !== null;
  let compare = aNotShorter - bNotShorter;
  switch (compare) {
    case -1: return b;
    case  1: return a;
    default: return null;
  }
}