How to check whether a string contains a substring in JavaScript?

To check whether a string contains a substring in JavaScript, you can use the includes method of the String object.

Here’s an example of how you can use the includes method to check whether a string contains a substring:

const str = 'Hello, World!';

if (str.includes('Hello')) {
  console.log('The string contains the substring.');
} else {
  console.log('The string does not contain the substring.');
}

This will check whether the string 'Hello, World!' contains the substring 'Hello', and print the appropriate message.

Alternatively, you can use the indexOf method of the String object to check for the presence of a substring:

const str = 'Hello, World!';

if (str.indexOf('Hello') !== -1) {
  console.log('The string contains the substring.');
} else {
  console.log('The string does not contain the substring.');
}

This will also check whether the string 'Hello, World!' contains the substring 'Hello', and print the appropriate message.

Keep in mind that both the includes and indexOf methods are case-sensitive, so they will not match substrings that differ in case. If you need to perform a case-insensitive search, you can use the toLowerCase or toUpperCase method to convert the string and the substring to the same case before checking for their presence.