Card Auto-selector (jQuery)

card.js

function detect_card(){
	var types = {
		Amex: [34,37],
		Visa: [4],
		Mastercard: [51, 52, 53, 54, 55],
		Discover: [6011]
	};
	
	//Loop the options and build a regexp
	$.each(types, function(i,opts){
		$.each(opts, function(i2,rexp){
			var re = new RegExp('^'+rexp);
			if ( $('#card_number').val().match(re) ) {
				//We have a match! Now find the correct card type
				$('#card_type > option').each(function(i3,elm){
					if ( $(elm).val() == i ) {
						$(elm).attr('selected', true);
					}
				});
			}
		});
	});
}

index.html

<input name="card_number" id="card_number" type="text" maxlength="255" style="width:208px;" onkeyup="detect_card();" />
<select name="card_type" id="card_type" style="width:120px;">
    <option value="0">----</option>
    <option value="Visa">Visa</option>
    <option value="Mastercard">Mastercard</option>
    <option value="Discover">Discover</option>
    <option value="Amex">Amex</option>
</select>