Rename js snippets

snippets/js/s/value-frequencies.md

@@ -0,0 +1,26 @@
+---
+title: Value frequencies
+type: snippet
+language: javascript
+tags: [array,object]
+author: chalarangelo
+cover: tropical-waterfall
+dateModified: 2020-10-19T22:49:51+03:00
+---
+
+Creates an object with the unique values of an array as keys and their frequencies as the values.
+
+- Use `Array.prototype.reduce()` to map unique values to an object's keys, adding to existing keys every time the same value is encountered.
+
+```js
+const frequencies = arr =>
+  arr.reduce((a, v) => {
+    a[v] = a[v] ? a[v] + 1 : 1;
+    return a;
+  }, {});
+```
+
+```js
+frequencies(['a', 'b', 'a', 'c', 'a', 'a', 'b']); // { a: 4, b: 2, c: 1 }
+frequencies([...'ball']); // { b: 1, a: 1, l: 2 }
+```