In D3 3.x, the only way to stop a timer was for the callback to return true. For example, this timer self-terminates after one second:
In D3 3.x, the only way to stop a timer was for its callback to return true. For example, this timer stops after one second:
```js
d3.timer(function(elapsed){
...
...
@@ -975,7 +975,7 @@ var t = d3.timer(function(elapsed) {
});
```
The primary benefit of this new design is that timers are not required to self-terminate: they can be stopped externally, allowing for the immediate and synchronous disposal of associated resources, and the separation of concerns. For example, the above is equivalent to:
The primary benefit of *timer*.stop is that timers are not required to self-terminate: they can be stopped externally, allowing for the immediate and synchronous disposal of associated resources, and the separation of concerns. The above is equivalent to:
```js
vart=d3.timer(function(elapsed){
...
...
@@ -987,7 +987,7 @@ d3.timeout(function() {
},1000);
```
This new design also improves[d3-transition](#transitions-d3-transition): now when a transition is interrupted, its resources are immediately freed rather than having to wait for transition to start!
This improvement extends to[d3-transition](#transitions-d3-transition): now when a transition is interrupted, its resources are immediately freed rather than having to wait for transition to start!
4.0 also introduces a new [*timer*.restart](https://github.com/d3/d3-timer#timer_restart) method for restarting timers, for replacing the callback of a running timer, or for changing delay and reference time. Unlike calling *timer*.stop and then creating a new timer, calling *timer*.restart maintains the invocation priority of an existing timer, so you can guarantee that the order of invocation of active timers will remain the same.
