How to decode the JWT encoded token payload on client-side in angular?

I am getting one JWT encoded access token from my API in response. But I am not able to decode it and get it in JSON format. I tried using the angular2-jwt library for it, but it did not worked. I am writing my code below:

 setXAuthorizationToken(client){
    let requestHeader = new Headers();
    requestHeader.append('Content-Type', 'application/x-www-form-urlencoded');
    this.http.post(client.clientURL + "oauth/token", 'grant_type=password&client_id=toto&client_secret=sec&' +  'username=' + client.username
    + '&password=' + client.password, {
      headers: requestHeader
    }).map(res=>res.json())
    .subscribe((token) =>{
      if(!token.access_token){
          return;
      }
      else{
       var decompressToken = LZString.decompressFromEncodedURIComponent(token.access_token);
       console.log(decompressToken);
}
    });
    }

Can anybody please help me solve this issue?

I use Auth0's jwt-decode package for decoding JWT token in Angular; this package works for me fine.

After installing the package through this command:

npm install jwt-decode

Import this package into your TypeScript class using this syntax:

import * as jwt_decode from "jwt-decode";

Or for newer versions (3 and above):

import jwt_decode from 'jwt-decode';

Then use this library method for decoding your access token like this:

getDecodedAccessToken(token: string): any {
  try {
    return jwt_decode(token);
  } catch(Error) {
    return null;
  }
}

The token parameter defines your access token which comes from your API.

The jwt_decode method returns the decoded token info as an object; you can access any info from your token.

Example

const tokenInfo = this.getDecodedAccessToken(token); // decode token
const expireDate = tokenInfo.exp; // get token expiration dateTime
console.log(tokenInfo); // show decoded token object in console

> jwt-decode is a small browser library that helps to decode JWTs token which is Base64Url encoded. > > IMPORTANT: This library doesn't validate the token, any well formed JWT can be decoded. You should validate the token in your > server-side logic by using something like express-jwt, koa-jwt, Owin > Bearer JWT, etc.

Try and use the JavaScript build in function atob(). Kind of like this:

atob(token.split('.')[1])

Notes:

> - The token is actually a string. > > - If you want to know why i split the token you should check this website jwt.io.

Use @auth0/angular-jwt

Step - 1 : Install using npm

npm install @auth0/angular-jwt

Step - 2 : Import the package

import { JwtHelperService } from '@auth0/angular-jwt';

Step - 3 : Create an instance and use

const helper = new JwtHelperService();

const decodedToken = helper.decodeToken(myRawToken);

// Other functions
const expirationDate = helper.getTokenExpirationDate(myRawToken);
const isExpired = helper.isTokenExpired(myRawToken);

atob function does not parse cyrillic or hebrew correctly so I must use JwtHelperService().decodeToken(token) instead.

I have defined my JWTService as below! Hope it helps. It is in TypeScript but can be used in vanilla javascript by just copying the code.

import { Injectable } from "@angular/core";

@Injectable()
export class JWTService {
    private chars: string = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
    private atob(input) {
        var str = String(input).replace(/=+$/, '');
        if (str.length % 4 == 1) {
            throw new Error("'atob' failed: The string to be decoded is not correctly encoded.");
        }
        for (
            // initialize result and counters
            var bc = 0, bs, buffer, idx = 0, output = '';
            // get next character
            buffer = str.charAt(idx++);
            // character found in table? initialize bit storage and add its ascii value;
            ~buffer && (bs = bc % 4 ? bs * 64 + buffer : buffer,
                // and if not first of each 4 characters,
                // convert the first 8 bits to one ascii character
                bc++ % 4) ? output += String.fromCharCode(255 & bs >> (-2 * bc & 6)) : 0
        ) {
            // try to find character in table (0-63, not found => -1)
            buffer = this.chars.indexOf(buffer);
        }
        return output;
    };

    parseJwt(token) {
        var base64Url = token.split('.')[1];
        var base64 = base64Url.replace(/-/g, '+').replace(/_/g, '/');
        var jsonPayload = decodeURIComponent(this.atob(base64).split('').map(function (c) {
            return '%' + ('00' + c.charCodeAt(0).toString(16)).slice(-2);
        }).join(''));

        return JSON.parse(jsonPayload);
    };
}

Store your token on login like this:

localStorage.setItem("token")

Then declare a variable like this

> decodeToken:any

and decode token by using the following code:

 this.decodedToken = this.jwtHelper.decodeToken(localStorage.setItem("token"));