Update join.md as suggested by @atomiks

snippets/join.md

@@ -3,11 +3,8 @@
 Is like `Array.join()` but with an additional argument of `end`(is equal to `separator` by default) which is used to separate the second to last and last items in the array. Returns `""` when the array is empty and the first item when the length of array is 1.
 
 ```js
-const join = (arr,separator = ',',end = separator ) => {
-      return arr.reduce((acc,val,i) => {
-       return  i == arr.length - 2 ? acc + val + end : i == arr.length - 1 ? acc + val : acc + val + separator
-     },'')
- }
+const join = (arr, separator = ',', end = separator) => 
+  arr.slice(0, arr.length - 1).join(separator) + end + arr[arr.length - 1]
 ```
 
 ```js