How to check whether a string contains a substring in JavaScript

In JavaScript, you can check whether a string contains a substring using the includes() method, which returns a boolean value true if the string contains the specified substring and false otherwise.

Here’s an example:

const str = "Hello, world!";
const substr = "world";

if (str.includes(substr)) {
  console.log(`"${str}" contains "${substr}"`);
} else {
  console.log(`"${str}" does not contain "${substr}"`);
}

This will output: "Hello, world!" contains "world".