delegate.js

function delegate(selector, handler) {
  return function(e) {
    var context = this;
    var target = e.target;
    var delegateEl = e.currentTarget;
    var matches = delegateEl.querySelectorAll(selector);
    for (var el = target; el.parentNode && el !== delegateEl; el = el.parentNode) {
      for (var i = 0; i < matches.length; i++) {
        if (matches[i] === el) {
          handler.call(context, e);
          return;
        }
      }
    }
  };
}