Update measure-time-taken-by-function.md

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atomiks
2017-12-15 08:43:47 +11:00
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### Measure time taken by function
Use `performance.now()` to get start and end time for the function, `console.log()` the time taken.
Pass a callback function as the argument.
Use `console.time()` and `console.timeEnd()` to measure the difference between the start and end times to determine how long the callback took to execute.
```js
const timeTaken = callback => {
const t0 = performance.now(), r = callback();
console.log(performance.now() - t0);
console.time('timeTaken');
const r = callback();
console.timeEnd('timeTaken');
return r;
};
// timeTaken(() => Math.pow(2, 10)) -> 1024 (0.010000000009313226 logged in console)
// timeTaken(() => Math.pow(2, 10)) -> 1024
// (logged): timeTaken: 0.02099609375ms
```