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Omer Elbaz
Omer Elbaz

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Protecting your JavaScript APIs

1. Introduction

What is a JSON Web Token?

A JSON Web Token, or JWT, is a JSON based open standard for creating access tokens that assert some number of claims. A claim is simply a statement about an entity, such as a user, and can be anything that the issuer wants to assert. For example, a claim could be that a user is over 18 years old or that they have verified their email address.

Why use JSON Web Tokens?

There are many reasons why you might want to use JSON Web Tokens to secure your API endpoints. First, they are easy to work with and understand. Second, they are signed, so you can be sure that the claims contained in them have not been tampered with. Finally, they are supported by a large number of libraries and frameworks, making it easy to integrate them into your application.

How do JSON Web Tokens work?

JSON Web Tokens consist of three parts: the header, the payload, and the signature. The header contains information about the token, such as the algorithm used to generate the signature. The payload is where the claims are contained. And finally, the signature is used to verify that the token has not been tampered with.
To generate a signature, the header and payload are combined and encoded using the algorithm specified in the header. Then a secret key is used to sign the encoded data. The signature is then appended to the header and payload to create the final token.
Whenever you want to verify the authenticity of a JSON Web Token, you first need to decode it using the same algorithm that was used to sign it. Then you can check the signature using the secret key to make sure that it matches what was originally generated. If it does, then you know that the token has not been tampered with and you can trust the claims contained within it.

Example: Securing an API Endpoint with JWT

Now let's take a look at an example of how you might use JSON Web Tokens to secure an API endpoint. In this example, we'll be using NodeJS and ExpressJS on the backend and AngularJS on the frontend. We'll also be using jsonwebtoken, which is a great library for working with JWT in JavaScript.

First, let's set up our ExpressJS server:

const express = require('express');
const app = express();
// Secret key for JWT signing and encryption
const SECRET_KEY = 'secretkey123456';
// Create express middleware that parses incoming
// HTTP requests with JSON payloads
// Create an endpoint for /login'/login', (req, res) => {
    // Generate JWT
    const jwt = require('jsonwebtoken');
    const token = jwt.sign({
        username: req.body.username
    }, SECRET_KEY);
    // Send back JWT
// Create an endpoint for /protected
app.get('/protected', (req, res) => {
    // Verify JWT
    if (!req.headers['authorization']) {
        return res.status(401).send({
            message: "You are not authorized"
    const jwt = require('jsonwebtoken');
    try {
        // Verify token
        var decoded = jwt.verify(req.headers['authorization'], SECRET_KEY);
        console.log("Decoded: ", decoded);
        res.send("You have access!");
    } catch (error) {
        console.log("Error: ", error);
        res.send("You are not authorized");
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2. Securing your JavaScript APIs

Authentication and Authorization

There are many ways to implement authentication and authorization in a JavaScript API. The most important thing is to make sure that your implementation is secure and that it meets the needs of your particular application.

Transport Layer Security

TLS and OAuth 2.0 are two important security protocols that are used to protect data and information exchanged over the Internet. TLS is a protocol that provides communication security over the Internet. OAuth 2.0 is an authorization framework that allows applications to obtain limited access to user accounts on an HTTP service.


There are several things to consider when choosing what type of cryptographic encryption to use:

  • The type of data you need to protect
  • The level of security you require
  • The amount of time and effort you are willing to put into implementation Once you have selected a cryptographic method, you need to implement it in your code. This can be a nontrivial task, so you may want to consider using a library or framework to help with implementation. Cryptography is a critical part of security for JavaScript APIs, so it is important to take the time to choose and implement an appropriate solution for your needs. And that's a wrap! By following the tips above, you can sleep soundly knowing that your JavaScript APIs are well-protected. So go forth and build those beautiful APIs, safe in the knowledge that they're well defended against the forces of evil.
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Discussion (1)

vjnvisakh profile image
Visakh Vijayan • Edited on

nice article. not production good code though :)