Update "Finders-keepers" guide index.md (#34217)

* Update index.md

My proposed advanced solution

* Update index.md

guide/english/certifications/javascript-algorithms-and-data-structures/basic-algorithm-scripting/finders-keepers/index.md

@@ -39,3 +39,19 @@ function findElement(arr, func) {
 * The `num` variable is being passed into the function, so we set it to each index in our array.
 * The pre-defined function already checks each number for us, so if it is "true", we return that num.
 * If none of the numbers in the array pass the function's test, we return undefined.
+
+
+## Advanced Solution
+
+```javascript
+function findElement(arr, func) {
+ return arr[(arr.map(func)).indexOf(true)];
+}
+```
+
+## Code Explanation
+
+1. Look through the array given in the 1st paramater "arr" using the .map() method
+2. Use the function in the 2nd parameter as the callback function in arr.map()
+3. Acquire the index of the first number that meets the condition in the function.
+4. Use that index to display the first available number that meets the condition.