JWT tokenize - Postman Pre-Request Script

pre-request-jwt.js

function base64url(source) {
	// Encode in classical base64
	encodedSource = CryptoJS.enc.Base64.stringify(source);

	// Remove padding equal characters
	encodedSource = encodedSource.replace(/=+$/, '');

	// Replace characters according to base64url specifications
	encodedSource = encodedSource.replace(/\+/g, '-');
	encodedSource = encodedSource.replace(/\//g, '_');

	return encodedSource;
}

function addIAT(request) {
	var iat = Math.floor(Date.now() / 1000) + 257;
	data.iat = iat;
	return data;
}


var header = {
	"typ": "JWT",
	"alg": "HS256"
};

var data = {
	"fname": "name",
	"lname": "name",
	"email": "email@domain.com",
	"password": "abc123$"
};

data = addIAT(data);

var secret = 'myjwtsecret';

// encode header
var stringifiedHeader = CryptoJS.enc.Utf8.parse(JSON.stringify(header));
var encodedHeader = base64url(stringifiedHeader);

// encode data
var stringifiedData = CryptoJS.enc.Utf8.parse(JSON.stringify(data));
var encodedData = base64url(stringifiedData);

// build token
var token = encodedHeader + "." + encodedData;

// sign token
var signature = CryptoJS.HmacSHA256(token, secret);
signature = base64url(signature);
var signedToken = token + "." + signature;

postman.setEnvironmentVariable("payload", signedToken);

In my case changed secret to base64 worked perfectly. Those who are facing problem can try this out

var signature = CryptoJS.HmacSHA256(token, CryptoJS.enc.Base64.parse(secret));