How to add konami code in a website based on html?

Question

I was asked to implement the Konami Code in a website I'm currently working on. It should do the following:

1. Change Background Image

2. Play sound

3. Bring some pop-up

What's the easiest way to achieve this using javascript?

Answer 1

Silentdrummer has a good answer. I'm not entirely sure, but I think it could end up taking up too much memory on typing intensive pages. It's good practice to reset. Either way, here's an alternative.

// Cheat Codes
neededkeys = [38,38,40,40,37,39,37,39,66,65], started = false, count = 0;
$(document).keydown(function(e) {
    key = e.keyCode;
    if (!started) {
        if (key == 38) {
            started = true;
        }
    }
    if (started) {
        if (neededkeys[count] == key) {
            count++;
        } else {
            reset();
        }
        if (count == 10) {
            reset();
            // Do your stuff here
            alert('Cheat Codes Activated');
            $('body').css('background-color', '#FFA8A8');
            // Turn down for what
            var s=document.createElement('script');
            s.setAttribute('src','https://nthitz.github.io/turndownforwhatjs/tdfw.js');
            document.body.appendChild(s);
        }
    } else {
        reset();
    }
});
function reset() {
    started = false;
    count = 0;
}