# 30 seconds of code

Back to Home#### hz

functionintermediateReturns the number of times a function executed per second.
`hz`

is the unit for `hertz`

, the unit of frequency defined as one cycle per second.

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.
Return the number of cycles per second by converting milliseconds to seconds and dividing it by the time elapsed.
Omit the second argument, `iterations`

, to use the default of 100 iterations.

const hz = (fn, iterations = 100) => { const before = performance.now(); for (let i = 0; i < iterations; i++) fn(); return (1000 * iterations) / (performance.now() - before); };