The indexOf() method in JavaScript is used to find a specified substring in a string and return its starting index. If the substring is not found, -1 is returned. The syntax is string.indexOf(substring[, startIndex]), and the parameters include the substring to be found and an optional starting index. This method is case-sensitive, supports forward search, and is suitable for scenarios where different strings are distinguished.
##indexOf() Usage in JavaScript
indexOf() Method is used to find the specified substring in a string and return the index position of its first match. If the substring is not found, -1 is returned.
Syntax:
string.indexOf(substring[, startIndex])
Parameters:
- substring: The substring to be found String.
- startIndex (optional): The index position at which to start the search (starting from 0).
Usage:
let str = "Hello World"; // 查找 "World" 的索引位置 console.log(str.indexOf("World")); // 6 // 从索引 2 开始查找 console.log(str.indexOf("World", 2)); // -1 // 查找不存在的子字符串 console.log(str.indexOf("JavaScript")); // -1
Features:
- It is case sensitive.
- If startIndex is less than 0, search starts from the beginning of the string.
- If startIndex is greater than the length of the string, -1 is returned.
- If the substring is the empty string, 0 is returned.
Example:
// 查找字符串中第一个 "e" 的索引位置 let str = "Elephant"; let index = str.indexOf("e"); // 如果找到子字符串,则打印其索引 if (index !== -1) { console.log(`找到 "e" 的索引位置:${index}`); }
Note:
indexOf() method for Unicode String support is limited. For more complex string searches, it is recommended to use the
search() method or regular expressions.
The above is the detailed content of Indexof usage in js. For more information, please follow other related articles on the PHP Chinese website!

Detailed explanation of JavaScript string replacement method and FAQ This article will explore two ways to replace string characters in JavaScript: internal JavaScript code and internal HTML for web pages. Replace string inside JavaScript code The most direct way is to use the replace() method: str = str.replace("find","replace"); This method replaces only the first match. To replace all matches, use a regular expression and add the global flag g: str = str.replace(/fi

So here you are, ready to learn all about this thing called AJAX. But, what exactly is it? The term AJAX refers to a loose grouping of technologies that are used to create dynamic, interactive web content. The term AJAX, originally coined by Jesse J

10 fun jQuery game plugins to make your website more attractive and enhance user stickiness! While Flash is still the best software for developing casual web games, jQuery can also create surprising effects, and while not comparable to pure action Flash games, in some cases you can also have unexpected fun in your browser. jQuery tic toe game The "Hello world" of game programming now has a jQuery version. Source code jQuery Crazy Word Composition Game This is a fill-in-the-blank game, and it can produce some weird results due to not knowing the context of the word. Source code jQuery mine sweeping game

Article discusses creating, publishing, and maintaining JavaScript libraries, focusing on planning, development, testing, documentation, and promotion strategies.

This tutorial demonstrates how to create a captivating parallax background effect using jQuery. We'll build a header banner with layered images that create a stunning visual depth. The updated plugin works with jQuery 1.6.4 and later. Download the

The article discusses strategies for optimizing JavaScript performance in browsers, focusing on reducing execution time and minimizing impact on page load speed.

Matter.js is a 2D rigid body physics engine written in JavaScript. This library can help you easily simulate 2D physics in your browser. It provides many features, such as the ability to create rigid bodies and assign physical properties such as mass, area, or density. You can also simulate different types of collisions and forces, such as gravity friction. Matter.js supports all mainstream browsers. Additionally, it is suitable for mobile devices as it detects touches and is responsive. All of these features make it worth your time to learn how to use the engine, as this makes it easy to create a physics-based 2D game or simulation. In this tutorial, I will cover the basics of this library, including its installation and usage, and provide a

This article demonstrates how to automatically refresh a div's content every 5 seconds using jQuery and AJAX. The example fetches and displays the latest blog posts from an RSS feed, along with the last refresh timestamp. A loading image is optiona


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

Dreamweaver CS6
Visual web development tools

WebStorm Mac version
Useful JavaScript development tools

Zend Studio 13.0.1
Powerful PHP integrated development environment

SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.

Safe Exam Browser
Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.