Add partition

snippets/partition.md

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+### partition
+
+Groups the elements into two arrays, depending on the provided function's truthiness for each element.
+
+Use `Array.reduce()` to create an array of two arrays.
+Use `Array.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) => {fn(val,i,arr) ? acc[0].push(val) : acc[1].push(val); return acc;},[[],[]]);
+```
+
+```js
+var 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 }]]
+```