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30-seconds-of-code/snippets/recordAnimationFrames.md
30secondsofcode 321bbe631b Travis build: 1778
2018-03-06 07:12:50 +00:00

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### recordAnimationFrames
Invokes the provided callback on each animation frame.
Use recursion.
Provided that `running` is `true`, continue invoking `window.requestAnimationFrame()` which invokes the provided callback.
Return an object with two methods `start` and `stop` to allow manual control of the recording.
Omit the second argument, `autoStart`, to implicitly call `start` when the function is invoked.
```js
const recordAnimationFrames = (callback, autoStart = true) => {
let running = true,
raf;
const stop = () => {
running = false;
cancelAnimationFrame(raf);
};
const start = () => {
running = true;
run();
};
const run = () => {
raf = requestAnimationFrame(() => {
callback();
if (running) run();
});
};
if (autoStart) start();
return { start, stop };
};
```
```js
const cb = () => console.log('Animation frame fired');
const recorder = recordAnimationFrames(cb); // logs 'Animation frame fired' on each animation frame
recorder.stop(); // stops logging
recorder.start(); // starts again
const recorder2 = recordAnimationFrames(cb, false); // `start` needs to be explicitly called to begin recording frames
```