jwt-user-helper

A lightweight, browser-friendly utility for handling JWT token generation, verification, storage in localStorage, and current user extraction. Designed for React, Next.js, or any frontend JavaScript project.

Features

• Generate JWT tokens
• Verify and decode tokens
• Save and retrieve tokens from localStorage
• Get current user info from JWT payload
• Logout / remove token
• Token expiry checker
• Works only in the browser (safe for SSR)

Installation

npm install jwt-user-helper

or

yarn add jwt-user-helper

Usage

Usage in Node.js | Server-side | React | Next.js

STEP 1: Mock localStorage BEFORE using the library

global.localStorage = {
  _data: {},
  setItem(key, value) {
    this._data[key] = value;
  },
  getItem(key) {
    return this._data[key];
  },
  removeItem(key) {
    delete this._data[key];
  },
};

STEP 2: Import the library

const {
  generateToken,
  saveToken,
  getCurrentUser,
  isAuthenticated,
  isTokenExpired,
  removeToken,
} = require("jwt-user-helper");

STEP 3: Define a secure secret key

const secret = "my_super_secure_secret_123";

STEP 4: Generate token with user payload and 1 hour expiration

const token = generateToken({ user: { id: 123, name: "Tariq" } }, secret, "1h");
console.log("Generated Token:", token);

STEP 5: Save token to localStorage

saveToken(token);
console.log("Token Saved:", token);

STEP 6: Get user from stored token

console.log("User:", getCurrentUser(secret)); // => { id: 123, name: "Tariq" }

STEP 7: Check authentication status

console.log("Is Authenticated?", isAuthenticated(secret)); // => true 

STEP 8: Check if token is expired

console.log("Is Token Expired?", isTokenExpired()); // => false

STEP 9: Logout (removes token)

removeToken();
console.log("Token Removed:", getCurrentUser(secret)); // => null

Usage in Browser

import {
  generateToken,
  saveToken,
  getCurrentUser,
  isAuthenticated,
  isTokenExpired,
  removeToken,
} from "jwt-user-helper";

const secret = "your_secure_key";
const token = generateToken({ user: { id: 1, name: "Alice" } }, secret, "1h");

saveToken(token);
console.log(getCurrentUser(secret)); // { id: 1, name: "Alice" }

API Reference

| Function | Description | | ------------------------------------------- | ---------------------------------- | | generateToken(payload, secret, expiresIn) | Generate a JWT token | | verifyToken(token, secret) | Verify and decode JWT | | saveToken(token) | Save to localStorage | | getToken() | Get token from storage | | removeToken() | Delete token | | getCurrentUser(secret) | Extract user from token | | isAuthenticated(secret) | Check if valid token exists | | isTokenExpired() | Returns true if token is expired |

Browser Compatibility

• Works in all modern browsers.
• Does not work in Node.js (uses localStorage).

Security

node -e "console.log(require('crypto').randomBytes(64).toString('hex'))"

License

MIT © Tariq Mehmood