Indexof usage in js

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:

<code class="javascript">string.indexOf(substring[, startIndex])</code>

Parameters:

• substring: The substring to be found String.
• startIndex (optional): The index position at which to start the search (starting from 0).

Usage:

<code class="javascript">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</code>

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:

<code class="javascript">// 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}`);
}</code>

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.

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