Messing around with closure
HTML
<button class="btn">button 1</button>
<button class="btn">button 2</button>
<button class="btn">button 3</button>
<button class="btn">button 4</button>
<button class="btn">button 5</button>
JavaScript
var buttons = document.querySelectorAll(".btn");
for (var i=0; i<buttons.length; i++) {
(function(lockedIn) {
buttons[i].onclick = function() {
alert(lockedIn);
};
})(i);
}