function (
  a,  // Node to delegate event to (I.E. document)
  b,  // Event to delegate (I.E. "click")
  c,  // Event handler function.
  d,  // CSS selectors to match the target child nodes.
  e,  // [optional] data to pass on to event handler.
  f   // (placeholder)
)
{
  f = a[                      // Cache old event.
    b = "on" + b              // Prepend "on" to event name.
  ];
  a[b] = function (g) {       // Set event to new function.
    if (g.target.matches(d))  // If we have a match for the selector
      c.call(g.target, g, e); // then call the event handler and pass on event and data.
    f ? f(g) : 0              // Chain call the cached event if there was one.
  }
}