Event delegation

gistfile1.js

function delegate(evt, parent, selector, fn) {
    parent.addEventListener(evt, function(e) {
        var elt = function find(el) {
            if (el.matchesSelector(selector)) {
                return el;
            }
            else {
                if (el.parentNode !== parent) {
                    return find(el.parentNode);
                }
                
                return false;
            }
        }(e.target);
        
        if (elt) {
            fn.call(elt, e);
        }
    }, false);
}