# Most performant function

JavaScript, Function · Oct 21, 2020

Returns the index of the function in an array of functions which executed the fastest.

- Use
`Array.prototype.map()`

to generate an array where each value is the total time taken to execute the function after`iterations`

times. - Use the difference in
`performance.now()`

values before and after to get the total time in milliseconds to a high degree of accuracy. - Use
`Math.min()`

to find the minimum execution time, and return the index of that shortest time which corresponds to the index of the most performant function. - Omit the second argument,
`iterations`

, to use a default of`10000`

iterations. - The more iterations, the more reliable the result but the longer it will take.

```
const mostPerformant = (fns, iterations = 10000) => {
const times = fns.map(fn => {
const before = performance.now();
for (let i = 0; i < iterations; i++) fn();
return performance.now() - before;
});
return times.indexOf(Math.min(...times));
};
```

```
mostPerformant([
() => {
// Loops through the entire array before returning `false`
[1, 2, 3, 4, 5, 6, 7, 8, 9, '10'].every(el => typeof el === 'number');
},
() => {
// Only needs to reach index `1` before returning `false`
[1, '2', 3, 4, 5, 6, 7, 8, 9, 10].every(el => typeof el === 'number');
}
]); // 1
```