Array.prototype.indexOf () - JavaScript | MDN
Jul 10, 2025 · The indexOf () method of Array instances returns the first index at which a given element can be found in the array, or -1 if it is not present.
JavaScript String indexOf () Method - W3Schools
Description The indexOf() method returns the position of the first occurrence of a value in a string. The indexOf() method returns -1 if the value is not found. The indexOf() method is case sensitive.
String.IndexOf Method (System) | Microsoft Learn
Reports the zero-based index of the first occurrence of the specified string in the current String object. Parameters specify the starting search position in the current string, the number of …
JavaScript String indexOf () Method
In this tutorial, you'll learn how to use the JavaScript String indexOf () method to find the index of a substring within a string.
How to Use indexOf() in JavaScript – Complete Guide with Examples
Jul 8, 2025 · Learn how to use indexOf () in JavaScript with syntax, examples, best practices, and comparisons with includes (). Perfect for beginners. Tagged with javascript, webdev, …
JavaScript Array indexOf () - Programiz
indexOf () Return Value Returns the first index of the element in the array if it is present at least once. Returns -1 if the element is not found in the array. Note: indexOf() compares …
JavaScript Array indexOf () Method - GeeksforGeeks
Sep 27, 2024 · The indexOf () method in JavaScript is used to find the position of the first occurrence of a specific value in an array. If the value is not present, it returns -1. This method …
JavaScript | Arrays | .indexOf() | Codecademy
Jun 21, 2021 · The .indexOf() method returns the first index at which a specified element can be found in an array, or -1 if the element is not present. This method searches the array from left …
JavaScript Array indexOf() method: Syntax, Usage, and Examples
The JavaScript array indexOf method is a quick and reliable way to determine the position of an element in an array, especially when working with primitive types like numbers and strings.
String.prototype.indexOf () - JavaScript | MDN - MDN Web Docs
Jul 10, 2025 · The indexOf() method of String values searches this string and returns the index of the first occurrence of the specified substring. It takes an optional starting position and returns …