jQuery plugin to detect Konami cheat code sequence

Question

How can this be written a bit shorter?

jQuery.konami = function(fn, code) {
 // ↑ ↑ ↓ ↓ ← → ← → B A
 code = code || [38, 38, 40, 40, 37, 39, 37, 39, 66, 65];
 var kkeys = '',
 i = 0;
 $(document).keydown(function(e) {
 var char = String.fromCharCode(e.which).toLowerCase();
 if (char === code[i++]) {
 kkeys += char;
 if (kkeys === code) {
 fn();
 kkeys = '';
 i = 0;
 }
 } else if (e.which === code[kkeys++]) {
 if (kkeys === code.length) {
 fn();
 kkeys = '';
 i = 0;
 }
 } else {
 kkeys = '';
 i = 0;
 }
 });
};

Answer 1

This is almost like code golf; this could probably be shortened. You just need to keep track of i and when it's past the end of the array, you know all the keys were hit in the correct order.

jQuery.konami = function() {
 function KonamiCode(kFn, kCode) {
 var i = 0;
 $(document).keydown(function(e) {
 var char = typeof kCode === 'string' ? String.fromCharCode(e.which).toLowerCase() : e.which;
 i = char === kCode[i] ? i + 1 : 0;
 if (i === kCode.length) {
 kFn();
 i = 0;
 }
 });
 }
 return function(fn, code) {
 // ↑ ↑ ↓ ↓ ← → ← → B A
 kCode = code || [38, 38, 40, 40, 37, 39, 37, 39, 66, 65];
 new KonamiCode(fn, kCode);
 };
}();

• yckart: nice approach, but works not as expected...
• Nick Larsen: @yckart what's wrong with it?
• user400654: yeah it just simply isn't working, :p jsfiddle.net/dxPdw/5 I haven't investigated as to why though
• yckart: @NickLarsen it breaks on multiple instantiations and even fails with strings (words)... jsfiddle.net/ARTsinn/dxPdw/6
• Nick Larsen: Silly logic error, i = char === code[i] ? 0 : i + 1; needed to be i = char === code[i] ? i + 1 : 0;.

Answer 2

Here's a slightly shortened version:

jQuery.konami = function(fn, code) {
 // ↑ ↑ ↓ ↓ ← → ← → B A
 code = code || [38, 38, 40, 40, 37, 39, 37, 39, 66, 65];
 var i = 0;
 $(document).keydown(function(e) {
 var char = $.type(code[i]) === "string" ? String.fromCharCode(e.which).toLowerCase() : e.which;
 if (char === code[i]) {
 i++;
 if (i == code.length) {
 fn();
 i = 0;
 }
 } else {
 i = 0;
 }
 });
};

the kkeys var wasn't needed, and you could move the if else into the retrieval of char, allowing you to reuse what was inside the if originally.

http://jsfiddle.net/dxPdw/12/

• yckart: Nice! However, got it already stackoverflow.com/questions/13647824/… ;-)