chooseBestSum.js

function chooseBestSum(t, k, ls) {
  let acc = [];
  generate(k, ls.length, [], ls, acc, 0, 0);
  const maxTravel = acc
    .map(chunk => chunk.reduce((acc, item) => acc += item))
    .filter(sum => sum <= t)
    .reduce((acc, sum) => {
      if (sum > acc) {
        acc = sum;
      }
      return acc;
    }, 0);
  return (maxTravel === 0) ? null : maxTravel;
}

function copy(arr) {
  return [].slice.call(arr);
}

function generate(m, n, chunk, a, acc, num, last) {
  if (num === m) {
    acc.push(copy(chunk));
  }
  
  for (let i = last + 1; i <= n; i++) {
    chunk.push(a[i - 1]);
    generate(m, n, chunk, a, acc, num + 1, i);
    chunk.pop();
  }
}