22 lines
586 B
Markdown
22 lines
586 B
Markdown
---
|
|
title: Apply function when condition is met
|
|
tags: function,logic
|
|
cover: flower-portrait-8
|
|
firstSeen: 2018-04-19T03:45:32+03:00
|
|
lastUpdated: 2020-10-22T20:24:44+03:00
|
|
---
|
|
|
|
Returns a function that takes one argument and runs a callback if it's truthy or returns it if falsy.
|
|
|
|
- Return a function expecting a single value, `x`, that returns the appropriate value based on `pred`.
|
|
|
|
```js
|
|
const when = (pred, whenTrue) => x => (pred(x) ? whenTrue(x) : x);
|
|
```
|
|
|
|
```js
|
|
const doubleEvenNumbers = when(x => x % 2 === 0, x => x * 2);
|
|
doubleEvenNumbers(2); // 4
|
|
doubleEvenNumbers(1); // 1
|
|
```
|