indexOfAll.md returns a functions with shadow vars

It returned a function that accepted the same arguments again that when run again with the same inputs would eventually result

snippets/indexOfAll.md

@@ -6,7 +6,7 @@ Use `Array.reduce()` to loop over elements and store indices for matching elemen
 Return the array of indices.
 
 ```js
-const indexOfAll = (arr, val) => (arr, val) =>
+const indexOfAll = (arr, val) =>
   arr.reduce((acc, el, i) => (el === val ? [...acc, i] : acc), []);
 ```