Rather than decorating the *dispatch* object with each event type, the dispatch object now exposes generic [*dispatch*.call](https://github.com/d3/d3-dispatch#dispatch_call) and [*dispatch*.apply](https://github.com/d3/d3-dispatch#dispatch_apply) methods which take the *type* string as the first argument. For example, to dispatch a *foo* event in D3 3.x, you might say:
```js
dispatcher.foo.call(that,"Hello, Foo!");
```
In D3 4.0, you’d say:
```js
dispatcher.call("foo",that,"Hello, Foo!");
```
The [*dispatch*.on](https://github.com/d3/d3-dispatch#dispatch_on) method now accepts multiple typenames, allowing you to add or remove listeners for multiple events simultaneously. For example, to send both *foo* and *bar* events to the same listener:
```js
dispatcher.on("foo bar",function(message){
console.log(message);
});
```
This matches the new behavior of [*selection*.on](https://github.com/d3/d3-selection#selection_on) in [d3-selection](#selections-d3-selection). The *dispatch*.on method now validates that the specifier *listener* is a function, rather than throwing an error in the future.
The new implementation d3.dispatch is faster, using fewer closures to improve performance. There’s also a new [*dispatch*.copy](https://github.com/d3/d3-dispatch#dispatch_copy) method for making a copy of a dispatcher. This is used by [d3-transition](#transitions-d3-transition) for copy-on-write semantics, improving the performance of transitions in common cases where all elements in a transition have the same set of transition event listeners.
