Function event

explainshell/web/static/js/d3.v3.js:382–386

()

  function d3_dispatch_event(dispatch) {
    var listeners = [], listenerByName = new d3_Map();
    function event() {
      var z = listeners, i = -1, n = z.length, l;
      while (++i < n) if (l = z[i].on) l.apply(this, arguments);
      return dispatch;
    }
    event.on = function(name, listener) {
      var l = listenerByName.get(name), i;
      if (arguments.length < 2) return l && l.on;