Added format number in JS

snippets/formatNumber.md

@@ -0,0 +1,17 @@
+---
+title: formatNumber
+tags: string,math,beginner
+---
+
+Returns a number using the local number format order.
+
+Use `Number.prototype.toLocaleString()` to convert a number to using the local number format separators.
+
+```js
+const formatNumber = number => number.toLocaleString();
+```
+
+```js
+formatNumber(123456); // '123,456' in `en-US`
+formatNumber(15675436903); // '15.675.436.903' in `de-DE`
+```