Creating JWT and signing it

Using module hmac256 to create JSON Web Token. A PR is wating for verification and comments.

const HMAC = require('hmac2256');
HmacSHA256 = function(token, secret) {
      var hmac = HMAC.SHA256(E.toArrayBuffer(secret));
     return btoa(String.fromCharCode.apply(null,  hmac.digest(E.toArrayBuffer(token)))).replace(/=+$/, ''); 
};

var header = { "alg": "HS256", "typ": "JWT"};
var data = { "id": 1337,"username": "john.doe"};
var secret = "My very confidential secret!";
var encodedHeader = btoa(JSON.stringify(header));
var encodedData = btoa(JSON.stringify(data));
var token = encodedHeader + "." + encodedData;
var signature = HmacSHA256(token, secret);
var jwt = (token+'.'+signature);