sumNestAr.js

function isInt(x) {
  return (typeof x === 'number') && (x % 1 === 0);
}

function flatten(ar) {
  return ar.reduce(function(prev, curr) {
    return prev.concat((Array.isArray(curr) ? flatten(curr) : curr));
  }, []);
}

function arraySum(i) {
  return flatten(i).reduce(function(prev, curr) {
    return isInt(curr) ? prev + curr : prev;
  });
}