Check CheckBox in GridView Row on Arrow key Press using JavaScript

i wanted to add it to this but it is not working

i would like on pressing arrow key down or up to automatically get the field chkrow which is a checkbox to automatically be update to true based on the arrow key that has been pressed but i would want to achieve this using javascript

please help

<script type="text/javascript">
    function enter(obj) {
        var tr = obj.parentNode.parentNode;
        var cellIndex = obj.parentNode.cellIndex;
        var rowIndex = obj.parentNode.parentNode.rowIndex;
        if (event.keyCode == 37) //Left
        {
            if (cellIndex > 0)
                tr.parentNode.rows[rowIndex].cells[cellIndex - 1].getElementsByTagName('INPUT')[0].focus();

            return;
        }
        if (event.keyCode == 38) //Up
        {
            if (rowIndex > 1)
                tr.parentNode.rows[rowIndex - 1].cells[cellIndex].getElementsByTagName('INPUT')[0].focus();

            return;
        }
        if (event.keyCode == 39) //Right
        {
            if (cellIndex < tr.cells.length - 1)
                tr.parentNode.rows[rowIndex].cells[cellIndex + 1].getElementsByTagName('INPUT')[0].focus();
     
            return;
        }
        if (event.keyCode == 40) //Down
        {
            if (rowIndex < tr.parentNode.rows.length - 1)
                tr.parentNode.rows[rowIndex + 1].cells[cellIndex].getElementsByTagName('INPUT')[0].focus();

            return;
        }
    };
   

</script>

if (event.keyCode == 37) //Left
{
    if (cellIndex > 0)
        tr.parentNode.rows[rowIndex].cells[cellIndex - 1].getElementsByTagName('INPUT')[0].focus();
        $(this).closest("tr").find('[id*=chkRow]').attr('checked', 'checked');
        return;
}