JSON Web Tokens (JWT) are a popular method for securely transmitting information between clients and servers. They're widely used in modern web applications, especially those built with React, Angular, or Vue.js. When working with JWT, you'll often need to decode them to extract the user's data. This is where the jwt-decode package comes in.

To get started, install the jwt-decode package using npm or yarn: npm install jsonwebtoken or yarn add jsonwebtoken. Then, import the package in your JavaScript file and use the decode() function to decode your JWT.

Here's a simple example:

const jwt = require('jsonwebtoken');  
const token = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaGFuIjoiMjMwfQ.SflKxwRJSMeKKF2qt4FN9q74thSjsoLHMhbA6vrUxoo';  
const decoded = jwt.decode(token);  
console.log(decoded);  

This will output the decoded JWT data as a JavaScript object.

Read more: Decoding JWT Tokens in JavaScript with jwt-decode