largest product of 4 numbers horizontally, vertically or diagonally

gistfile1.txt

let colLarge = [
  [1,1,1,1,1,4],
  [1,1,1,1,1,4],
  [1,1,1,1,1,4],
  [1,1,1,1,1,4],
  [1,1,1,1,1,1],
  [1,1,1,1,1,1]
]

let rowLarge = [
  [1,1,1,1,1,1],
  [1,1,1,1,1,1],
  [1,1,1,1,1,1],
  [1,1,5,5,5,5],
  [1,1,1,1,1,1],
  [1,1,1,1,1,1]
]

let diagLarge = [
  [1,1,1,1,1,1],
  [1,6,1,1,1,1],
  [1,1,6,1,1,1],
  [1,1,1,6,1,1],
  [1,1,1,1,6,1],
  [1,1,1,1,1,1]
]

function findLargest(data) {
  let largest = 0;
  for(var i = 0; i < data.length; i++) {
    for(var j = 0; j < data[i].length; j++) {
      let horizontal = vertical = diagonal = data[i][j];
      for(var k = 1; k < 4; k++) {
        if(j < data[i].length - 3) horizontal = horizontal * data[i][j + k];
        if(j < data[i].length - 3 && i < data.length - 3) diagonal = diagonal * data[i + k][j + k];
        if(i < data.length - 3) vertical = vertical * data[i + k][j];
      }
      if(horizontal > largest) largest = horizontal;
      if(diagonal > largest) largest = diagonal;
      if(vertical > largest) largest = vertical;
    }
  }
  return largest;
}

const col = findLargest(colLarge);
const row = findLargest(rowLarge);
const diag = findLargest(diagLarge);

console.log(col);
console.log(row);
console.log(diag);