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How to use contains in js

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contains method is used in JavaScript to check whether a string contains another string and returns a Boolean value (true or false). The syntax is: string.contains(substring), where string is the target string and substring is the substring to be found.

How to use contains in js

Using the contains method in JavaScript

What is the contains method?

contains method is used to check whether a string contains another string and returns a Boolean value: true or false.

Syntax

string.contains(substring)

Where:

  • string is the target string to be checked.
  • substring is the substring to be found.

Usage

The use of the contains method is very simple:

  1. Store the target string in a variable.
  2. Call the contains method, passing the substring as a parameter.
  3. Store the returned Boolean value in a variable or use it directly.

Example:

// 检查字符串是否包含另一个字符串
const message = "Hello, world!";
const result = message.contains("world");

console.log(result); // 输出:true

Notes

  • contains method is case-sensitive.
  • Substring can be of any length, including the empty string.
  • If the target string is null or undefined, the contains method will return false.

Alternative methods

Besides the contains method, there are other ways to check if a string contains another string:

  • indexOf: If the substring exists, return the index of the first occurrence of the substring in the target string, otherwise return -1.
  • includes: Similar to contains, but it accepts an optional starting index parameter.

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