Rename js snippets

snippets/js/s/partition-array-in-two.md

@@ -0,0 +1,36 @@
+---
+title: Partition array in two
+type: snippet
+language: javascript
+tags: [array,object]
+cover: camping-trip
+dateModified: 2020-11-03T21:46:13+02:00
+---
+
+Groups the elements into two arrays, depending on the provided function's truthiness for each element.
+
+- Use `Array.prototype.reduce()` to create an array of two arrays.
+- Use `Array.prototype.push()` to add elements for which `fn` returns `true` to the first array and elements for which `fn` returns `false` to the second one.
+
+```js
+const partition = (arr, fn) =>
+  arr.reduce(
+    (acc, val, i, arr) => {
+      acc[fn(val, i, arr) ? 0 : 1].push(val);
+      return acc;
+    },
+    [[], []]
+  );
+```
+
+```js
+const users = [
+  { user: 'barney', age: 36, active: false },
+  { user: 'fred', age: 40, active: true },
+];
+partition(users, o => o.active);
+// [
+//   [{ user: 'fred', age: 40, active: true }],
+//   [{ user: 'barney', age: 36, active: false }]
+// ]
+```