Merge array of arrays and sort the output array based on last index

var array1 = [
  [10, 25, 30, 55, 1],
  [3, 15, 67, 78, 2],
  [45, 67, 55, 65, 4]
];

var array2 = [
  [10, 25, 30, 55, 2],
  [3, 15, 67, 78, 3],
  [45, 67, 55, 65, 4],
  [61, 76, 87, 56, 5]
];

console.log(array1);
console.log(array2);

function getArrayWhenLastElementMatches(targetArray, value) {
  var matchedElements = targetArray.find(function (array) {
    return array[array.length - 1] === value;
  });
  matchedElements = matchedElements
    ? matchedElements
    : Array(targetArray[0].length).fill(null);
  return matchedElements;
}
var array3 = array1.concat(array2);
var array3LastIndexElements = array3.map((array) => array[array.length - 1]);
var newArraySize = Math.max(...array3LastIndexElements);
var newArray = [];
for (let arrayIndex = 1; arrayIndex <= newArraySize; arrayIndex++) {
  var arrayWhenLastElementMatchesInArray1 = getArrayWhenLastElementMatches(
    array1,
    arrayIndex
  );
  var arrayWhenLastElementMatchesInArray2 = getArrayWhenLastElementMatches(
    array2,
    arrayIndex
  );
  newArray.push(
    arrayWhenLastElementMatchesInArray1.concat(
      arrayWhenLastElementMatchesInArray2
    )
  );
}
console.log(newArray);