In JavaScript, you can check whether a string contains a substring using several methods. Here are some common approaches:
The indexOf() method returns the index within the string of the first occurrence of the specified substring, or -1 if the substring is not found.
Example:
const str = 'Hello, world!'; const substring = 'world'; if (str.indexOf(substring) !== -1) { console.log('Substring found'); } else { console.log('Substring not found'); }
The includes() method determines whether a string contains the specified substring. It returns true if the substring is found, otherwise false.
Example:
const str = 'Hello, world!'; const substring = 'world'; if (str.includes(substring)) { console.log('Substring found'); } else { console.log('Substring not found'); }
You can also use regular expressions to check for substrings within a string.
Example:
const str = 'Hello, world!'; const substring = 'world'; const regex = new RegExp(substring); if (regex.test(str)) { console.log('Substring found'); } else { console.log('Substring not found'); }