Consistency for snippet highlighting

README.md

@@ -640,7 +640,7 @@ const tail = arr => arr.length > 1 ? arr.slice(1) : arr;
 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...'

snippets/truncate-a-string.md

@@ -3,7 +3,7 @@
 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...'