Return an array consisting of the largest number from each provided sub-array.

bonfire-return-largest-numbers-in-arrays.js

// Bonfire: Return Largest Numbers in Arrays
// Author: @joepichardo
// Challenge: http://www.freecodecamp.com/challenges/bonfire-return-largest-numbers-in-arrays
// Learn to Code at Free Code Camp (www.freecodecamp.com)

function largestOfFour(arr) {
  // You can do this!
  //empty array to place new numbers in
  var largestArray = [];
  var largestNumber = 0;
  /*
  two for loops go through the two-dimensional array
  compares numbers within each sub-array to find the largest number
  that number is then placed into our array
  largestNumber is equaled to 0 after the second for loop is 
  finished so the next comparison is ready to go
  */
  for(var i = 0; i < arr.length ;i++){
    for(var j = 0; j < arr[i].length; j++){
      if(arr[i][j] > largestNumber){
        largestNumber = arr[i][j];
        largestArray[i] = largestNumber;
      }
    }
    largestNumber = 0;
  }
  
  return largestArray;
}

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