fix: update article for JavaScript String.indexOf() (#36012)

* fix: update article for JavaScript String.indexOf()

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

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

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

@@ -2,7 +2,8 @@
 title: String.prototype.indexOf
 ---
 ## String.prototype.indexOf
-The `indexOf()` method returns the first index at which a given element can be found in the array. If the element is not present, it returns -1.
+
+The `indexOf()` method returns the first index at which a specified string can be found in the given String object. If the string is not present, it returns -1.
 
 **Syntax**
 ```javascript
@@ -10,17 +11,25 @@ str.indexOf(searchValue[, fromIndex])
 ```
 
 ### Parameters
-*   **searchValue** Substring for which you are looking. If this is empty (`''`) and there is no `fromIndex` parameter, this will return 0.
+*   **searchValue** Substring for which you are looking. If this is empty (`''`) and there is no `fromIndex` argument, `indexOf()` will return 0.
 
-*   **fromIndex** Optional. The index at which you want to start the search. If the `fromIndex` value is greater than or equal to the string's length, the string is not searched and the method returns -1. If the `searchValue` is an empty string (`''`) and the `fromIndex` is less than the string's length, it will return the `fromIndex`; otherwise, it will return the string's length. (A negative number will be treated as though there is no argument.)
+*   **fromIndex** Optional. The index at which you want to start the search from. The default value is 0.
+    * If `fromIndex` is negative, the string will be searched from the beginning.
+    * If `fromIndex` is less than the string's length:
+        * If `searchValue` is not an empty string (`''`), the string will be searched 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 string is not searched and the method returns -1.
+        * If `searchValue` is an empty string (`''`), the method returns the string's length.
 
 ### Description
-The `indexOf()` method checks the string from left to right. The index of the first character is 0; the index of the last character is ``string.length - 1``. The method checks each substring against `searchValue` using strict equality (`===`), which means this method is case sensitive. Once it finds a substring that returns `true`, it returns the index of its first character.
+The `indexOf()` method checks the string from left to right. 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'.indexOf('Blue');     // returns  0
 'Blue Whale'.indexOf('Blute');    // returns -1
+'Blue Whale'.indexOf('blue');     // returns -1
 'Blue Whale'.indexOf('Whale', 0); // returns  5
 'Blue Whale'.indexOf('Whale', 5); // returns  5
 'Blue Whale'.indexOf('Whale', 7); // returns -1
@@ -28,9 +37,7 @@ The `indexOf()` method checks the string from left to right. The index of the fi
 'Blue Whale'.indexOf('', 9);      // returns  9
 'Blue Whale'.indexOf('', 10);     // returns 10
 'Blue Whale'.indexOf('', 11);     // returns 10
-'Blue Whale'.indexOf('blue');     // returns -1
 ```
 
 ### More Information:
-- MDN documentation: <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/indexOf' target='_blank' rel='nofollow'>MDN</a>
+- [String.prototype.indexOf() on MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/indexOf)
-- MSDN documentation: <a href='https://docs.microsoft.com/en-us/scripting/javascript/reference/indexof-method-string-javascript' target='_blank' rel='nofollow'>MSDN</a>