Consistency for snippet highlighting

snippets/truncate-a-string.md

@@ -1,9 +1,9 @@
 ### Truncate a String
 
-Determine if the string's `length` is greater than `num`. 
+Determine if the string's `length` is greater than `num`.
 Return the string truncated to the desired length, with `...` appended to the end or the original string.
 
-```
+```js
 const truncate = (str, num) =>
   str.length > num ? str.slice(0, num > 3 ? num-3 : num) + '...' : str;
 // truncate('boomerang', 7) -> 'boom...'