39 lines
1.2 KiB
Markdown
39 lines
1.2 KiB
Markdown
---
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title: hz
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tags: function,intermediate
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---
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Returns the number of times a function executed per second.
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`hz` is the unit for `hertz`, the unit of frequency defined as one cycle per second.
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- Use `performance.now()` to get the difference in milliseconds before and after the iteration loop to calculate the time elapsed executing the function `iterations` times.
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- Return the number of cycles per second by converting milliseconds to seconds and dividing it by the time elapsed.
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- Omit the second argument, `iterations`, to use the default of 100 iterations.
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```js
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const hz = (fn, iterations = 100) => {
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const before = performance.now();
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for (let i = 0; i < iterations; i++) fn();
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return (1000 * iterations) / (performance.now() - before);
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};
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```
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```js
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// 10,000 element array
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const numbers = Array(10000)
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.fill()
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.map((_, i) => i);
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// Test functions with the same goal: sum up the elements in the array
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const sumReduce = () => numbers.reduce((acc, n) => acc + n, 0);
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const sumForLoop = () => {
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let sum = 0;
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for (let i = 0; i < numbers.length; i++) sum += numbers[i];
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return sum;
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};
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// `sumForLoop` is nearly 10 times faster
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Math.round(hz(sumReduce)); // 572
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Math.round(hz(sumForLoop)); // 4784
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```
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