Swap, anagrams, occurences

Fixed sorting title for strings.

snippets/count-occurences-of-a-value-in-array.md

@@ -0,0 +1,7 @@
+### Count occurences of a value in array
+
+Use `filter()` to create an array containing only the items with the specified value, count them using `length`.
+
+```js
+var countOccurences = (arr, value) => arr.filter(v => v === value).length;
+```