Build an array with the max value of another set of arrays. Uses Math.max.apply

new_gist_file.js

function getLargest(arr) {
  var largestArr = [];
  
  for (var i = 0; i < arr.length; i++) {
    largestArr.push(Math.max.apply(null, arr[i]));
  }
  
  return largestArr;
}

getLargest([[4, 5, 1, 3], [13, 27, 18, 26], [32, 35, 37, 39], [1000, 1001, 857, 1]]);