feat: add article for JavaScript String.lastIndexOf() (#36013)

* feat: add article for JavaScript String.lastIndexOf()

* Update guide/english/javascript/standard-objects/string/string-prototype-lastindexof/index.md

Co-Authored-By: Tom <20648924+moT01@users.noreply.github.com>

guide/english/javascript/standard-objects/string/string-prototype-lastindexof/index.md

@@ -3,13 +3,41 @@ title: String.prototype.lastIndexOf
 ---
 ## String.prototype.lastIndexOf
 
-This is a stub. <a href='https://github.com/freecodecamp/guides/tree/master/src/pages/javascript/standard-objects/string/string-prototype-lastindexof/index.md' target='_blank' rel='nofollow'>Help our community expand it</a>.
+The `lastIndexOf()` method returns the first index at which the last occurrence of a specified string can be found in the given String object. If the string is not present, it returns -1.
 
-<a href='https://github.com/freecodecamp/guides/blob/master/README.md' target='_blank' rel='nofollow'>This quick style guide will help ensure your pull request gets accepted</a>.
+**Syntax**
+```javascript
+str.lastIndexOf(searchValue[, fromIndex])
+```
 
-<!-- The article goes here, in GitHub-flavored Markdown. Feel free to add YouTube videos, images, and CodePen/JSBin embeds  -->
+### Parameters
+*   **searchValue** Substring for which you are looking. If this is empty (`''`) and there is no `fromIndex` argument, `lastIndexOf()` will return the string's length.
 
-#### More Information:
+*   **fromIndex** Optional. The index at which you want to start the search backwards from. The default value is the string's length.
-<!-- Please add any articles you think might be helpful to read before writing the article -->
+    * If `fromIndex` is negative, the method will behave as though it were 0.
+    * If `fromIndex` is less than the string's length:
+        * If `searchValue` is not an empty string (`''`), the string will be searched backwards from `fromIndex`.
+        * If `searchValue` is an empty string (`''`), the method returns `fromIndex`.
+    * If `fromIndex` is greater than or equal to the string's length:
+        * If `searchValue` is not an empty string (`''`), the method will behave as though it were the string's length.
+        * If `searchValue` is an empty string (`''`), the method returns the string's length.
 
+### Description
+The `lastIndexOf()` method checks the string from right to left. The index of the first character is 0 and the index of the last character is ``string.length - 1``. The method checks each substring against `searchValue` using strict equality (`===`), which means that this method is case sensitive. Once it finds a substring that returns `true`, it returns the index of its first character.
 
+### Examples
+```javascript
+'Blue Whale'.lastIndexOf('Blue');     // returns  0
+'Blue Whale'.lastIndexOf('Blute');    // returns -1
+'Blue Whale'.lastIndexOf('blue');     // returns -1
+'Blue Whale'.lastIndexOf('Whale', 0); // returns -1
+'Blue Whale'.lastIndexOf('Whale', 5); // returns  5
+'Blue Whale'.lastIndexOf('Whale', 7); // returns  5
+'Blue Whale'.lastIndexOf('');         // returns 10
+'Blue Whale'.lastIndexOf('', 9);      // returns  9
+'Blue Whale'.lastIndexOf('', 10);     // returns 10
+'Blue Whale'.lastIndexOf('', 11);     // returns 10
+```
+
+### More Information:
+- [String.prototype.lastIndexOf() on MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/lastIndexOf)