javascript - How to check whether an array contains an element

I'd like to restrict keys that can be pressed.

$('.txtComments').keydown(function (event) {
  var keys = new Array();

  keys[0] = "8";
  keys[1] = "46";
  keys[2] = "37"
  keys[3] = "39"

  if(!(....)) //Check whether the keyCode is either of 8, 46, 37, or 39. 
  {
     event.preventDefault();  
  }
});

Thanks for helping

Answer

There are so many ways to implement this:

Just hard code it:

var keyCode = event.which;


if (keyCode != 8 && keyCode != 46 ...)

or check an array:

var keys = [8, 46, ...];
if (keys.indexOf(keyCode) < 0)

or the jQuery equivalent:

if ($.inArray(keyCode, keys) < 0)

or check an object:

var keys = { 8: 1, 46: 1, ... }
if (! (keyCode in keys) )  // or if (!keys[keyCode])

or a switch:

switch (keyCode) {
    case 8: case 46: ...
        // do nothing
        break;
    default:
        event.preventDefault();
}