Adds intermediate solution and corrects "run code" link (#18601)

* Correct "Run Code Link"

Currently when the user hits "Run Code" they are brought to a repl that shows a function for `reverseString`.  I just copied the code from the explanation into a new repl and linked that so when users click "Run code" they are taken to the correct code.

* Adds an intermediate solution

Since submitting my last PR on this page I have verified that my intermediate solution works, it eliminates the need for the `for` loop.

* fix: formatting

client/src/pages/guide/english/certifications/javascript-algorithms-and-data-structures/basic-algorithm-scripting/slice-and-splice/index.md

@@ -39,18 +39,18 @@ Increment the index after performing the splice.
 **Solution ahead!**
 
 ## ![:beginner:](https://forum.freecodecamp.com/images/emoji/emoji_one/beginner.png?v=3 ":beginner:") Basic Code Solution:
-
-    function frankenSplice(arr1, arr2, n) {
-      // It's alive. It's alive!
-      let localArray = arr2.slice();
-      for (let i = 0; i < arr1.length; i++) {
-        localArray.splice(n, 0, arr1[i]);
-        n++;
-      }
-      return localArray;
-    }
-
-![:rocket:](https://forum.freecodecamp.com/images/emoji/emoji_one/rocket.png?v=3 ":rocket:") <a href='https://repl.it/CLjU' target='_blank' rel='nofollow'>Run Code</a>
+```js
+function frankenSplice(arr1, arr2, n) {
+  // It's alive. It's alive!
+  let localArray = arr2.slice();
+  for (let i = 0; i < arr1.length; i++) {
+    localArray.splice(n, 0, arr1[i]);
+    n++;
+  }
+  return localArray;
+}
+```
+![:rocket:](https://forum.freecodecamp.com/images/emoji/emoji_one/rocket.png?v=3 ":rocket:") <a href='https://repl.it/repls/RedundantGrossGenres' target='_blank' rel='nofollow'>Run Code</a>
 
 ### Code Explanation:
 
@@ -64,6 +64,24 @@ Increment the index after performing the splice.
 
 * Finally, we return the `localArray` and end the function. 
 
+
+## 🌻 Intermediate Code Solution:
+```js
+function frankenSplice(arr1, arr2, n) {
+  // It's alive. It's alive!
+  let localArr = arr2.slice();
+  localArr.splice(n, 0, ...arr1);
+  return localArr;
+}
+```
+![:rocket:](https://forum.freecodecamp.com/images/emoji/emoji_one/rocket.png?v=3 ":rocket:") <a href='https://repl.it/repls/BelovedNegativeMoto' target='_blank' rel='nofollow'>Run Code</a>
+
+* Since our goal is to return the new array with out altering `arr1` or `arr2` we create a `localArr` and add all the items from `arr2` using the `slice()` function
+
+* Since the `splice()` function will mutate (alter) arrays and can be used to add new elements we will use it to add the contents of `arr1` into `localArr`.  `n` is the starting position where our content will be inserted.  We won't be deleting any elements so the next argument is `0`.  Then we add the entire contents of `arr1` using spread syntax `...`.
+
+* `localArr` is returned and the function is complete.
+
 ## ![:clipboard:](https://forum.freecodecamp.com/images/emoji/emoji_one/clipboard.png?v=3 ":clipboard:") NOTES FOR CONTRIBUTIONS:
 
 *   ![:warning:](https://forum.freecodecamp.com/images/emoji/emoji_one/warning.png?v=3 ":warning:") **DO NOT** add solutions that are similar to any existing solutions. If you think it is **_similar but better_**, then try to merge (or replace) the existing similar solution.