javascript keydown arow

1//detecting arrow key presses
2document.addEventListener('keydown', function(e) {
3    switch (e.keyCode) {
4        case 37:
5            alert('left');
6            break;
7        case 38:
8           alert('up');
9            break;
10        case 39:
11            alert('right');
12            break;
13        case 40:
14            alert('down');
15            break;
16    }
17});

1document.onkeydown = checkKey;
2
3function checkKey(e) {
4
5    e = e || window.event;
6
7    if (e.keyCode == '38') {
8        // up arrow
9    }
10    else if (e.keyCode == '40') {
11        // down arrow
12    }
13    else if (e.keyCode == '37') {
14       // left arrow
15    }
16    else if (e.keyCode == '39') {
17       // right arrow
18    }
19
20}