[Jcbones]

// check to make sure that the browser can handle window.addEventListener
if (window.addEventListener) {
    // create the keys and konami variables
    var keys = [],
        konami = "38,38,40,40,37,39,37,39,66,65";
 
    // bind the keydown event to the Konami function
    window.addEventListener("keydown", function(e){
        // push the keycode to the 'keys' array
        keys.push(e.keyCode);
 
        // and check to see if the user has entered the Konami code
        if (keys.toString().indexOf(konami) >= 0) {
            // add Easter Egg here:
 
            // and finally clean up the keys array
            keys = [];
        };
    }, true);
}; 

Found at:

Matt Kirman / How to recreate the Konami code in Javascript