Update snippet descriptions

snippets/last.md

@@ -5,7 +5,8 @@ tags: array,beginner
 
 Returns the last element in an array.
 
-- Check if `arr` is truthy and has a `length` property, use `arr.length - 1` to compute the index of the last element of the given array and return it, otherwise return `undefined`.
+- Check if `arr` is truthy and has a `length` property.
+- Use `Array.prototype.length - 1` to compute the index of the last element of the given array and return it, otherwise return `undefined`.
 
 ```js
 const last = arr => (arr && arr.length ? arr[arr.length - 1] : undefined);