Увеличение длины на элемента на JavaScript

const KEY_LEFT = 37; 
const KEY_UP = 38; 
const KEY_RIGHT = 39; 
const KEY_DOWN = 40 
var vendors = ["webkit", "moz", "o", "ms"]; 
for (var x = 0; x < vendors.length && !window.requestAnimationFrame; x++) { 
  window.requestAnimationFrame = window[vendors[x] + "RequestAnimationFrame"]; 
  window.cancelAnimationFrame = window[vendors[x] + "CancelAnimationFrame"] || 
    window[vendors[x] + "CancelRequestAnimationFrame"]; 
} 
var table = document.getElementById('table'); 
var rows = ''; 
for (var i = 0; i <= 15; i++) { 
  rows += '<tr class="row" + i'; 
  for (var j = 0; j <= 25; j++) { 
    rows += '<td></td>'; 
  } 
  rows += '</tr>'; 
} 
table.innerHTML = rows; 
var i = 0; 
var j = 0; 
 
function move(i, j) { 
  var old = document.querySelector("td.red"); 
  //console.log(i, j); 
  if (old) 
    old.classList.remove("red"); 
  table.rows[i].cells[j].classList.add("red"); 
} 
addEventListener("keydown", function(event) { 
  if (event.keyCode == KEY_UP) { // up 
    i--; 
    if (i < 0) 
      i = table.rows.length - 1; 
  } else if (event.keyCode == KEY_DOWN) { // down 
    i++; 
    if (i >= table.rows.length) 
      i = 0; 
  } else if (event.keyCode == KEY_RIGHT) { // right 
    j++; 
    if (j >= table.rows[0].cells.length) 
      j = 0; 
  } else if (event.keyCode == KEY_LEFT) { // left 
    j--; 
    if (j < 0) 
      j = table.rows[0].cells.length - 1; 
  } 
  move(i, j); 
}); 
move(i, j); 
 
function randomFood(i, j) { 
  var food = document.querySelector("td.green"); 
  if (food) 
    food.classList.remove("green"); 
  table.rows[i].cells[j].classList.add("green"); 
} 
randomFood(5, 8);

#table { 
  margin: 0 auto; 
} 
 
td { 
  width: 20px; 
  height: 20px; 
  border: 1px solid black; 
} 
 
td.red { 
  background: red; 
} 
 
td.green { 
  background: green; 
}

<table id="table"> 
  <tr class="row"> 
    <td></td> 
  </tr> 
</table>