Rename js snippets

snippets/js/s/conditionally-apply-function.md

@@ -0,0 +1,22 @@
+---
+title: Apply function when condition is met
+type: snippet
+language: javascript
+tags: [function,logic]
+cover: flower-portrait-8
+dateModified: 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
+```