update snippets 47-62

snippets/groupBy.md

@@ -9,6 +9,9 @@ Use `Array.reduce()` to create an object, where the keys are produced from the m
 const groupBy = (arr, func) =>
   arr.map(typeof func === 'function' ? func : val => val[func])
     .reduce((acc, val, i) => { acc[val] = (acc[val] || []).concat(arr[i]); return acc; }, {});
-// groupBy([6.1, 4.2, 6.3], Math.floor) -> {4: [4.2], 6: [6.1, 6.3]}
-// groupBy(['one', 'two', 'three'], 'length') -> {3: ['one', 'two'], 5: ['three']}
+```
+
+```js
+groupBy([6.1, 4.2, 6.3], Math.floor) -> {4: [4.2], 6: [6.1, 6.3]}
+groupBy(['one', 'two', 'three'], 'length') -> {3: ['one', 'two'], 5: ['three']}
 ```