Code to use Log In with PayPal in Node.js apps. Uses request and querystring and runs on the express framework.

liwpp.js

'use strict';

var request = require('request');
var querystring = require('querystring');

/*
 * CLIENT DETAILS
 */

var CLIENT_ID = "CLIENT_ID_HERE";
var CLIENT_SECRET = "CLIENT_SECRET_HERE";
var REDIRECT_URI = "http://yourAwesomeSite:3000/myCallback";
var SCOPE = "openid profile email address";

/*
 * ENDPOINTS LOG IN WITH PAYPAL
 */

var base_webapps = 'https://www.paypal.com/webapps/auth/protocol/openidconnect/v1';
var base_api = 'https://api.paypal.com/v1/identity/openidconnect';
var endpoint_authorize = base_webapps + '/authorize';
var endpoint_endsession = base_webapps + '/endsession';
var endpoint_tokenservice = base_api + '/tokenservice';
var endpoint_userinfo = base_api + '/userinfo';

/*
 * PLACEHOLDERS & CONSTANTS
 */

var TYPE_JSON = 'json';
var TYPE_FORM = 'form';

var user = {};

var token = {
  access_token: "",
  refresh_token: "",
  id_token: ""
};

var headers = {
  "Accept": "application/json",
  "Content-type": "application/json;charset=UTF-8",
  "Authorization": "Bearer " + token.access_token
};

exports.login = function (req, res) {
  var data = {
    client_id: CLIENT_ID,
    response_type: "code",
    scope: SCOPE,
    redirect_uri: REDIRECT_URI
  };

  res.redirect(endpoint_authorize + "?" + querystring.stringify(data));
};

exports.auth = function (req, res) {
  var data = {
    client_id: CLIENT_ID,
    client_secret: CLIENT_SECRET,
    grant_type: "authorization_code",
    code: req.query.code
  };

  doPost(endpoint_tokenservice, data, TYPE_FORM, function (error, response, body) {
    if (!error) {
      token = JSON.parse(body);
      headers.Authorization = "Bearer " + token.access_token;
      res.redirect("/profile");
    }
  });
};

exports.profile = function (req, res) {
  var data = {
    schema: "openid",
    access_token: token.access_token
  };

  doPost(endpoint_userinfo, data, TYPE_FORM, function (error, response, body) {
    if (!error && response.statusCode === 200) {
      user = JSON.parse(body);

      // do amazing stuff here
    }
  });
};

function doPost(url, data, type, callback) {
  if (type === 'json') {
    request.post({url: url, json: data, headers: headers }, callback);
  } else {
    request.post({url: url, form: data, headers: headers }, callback);
  }
}

function doGet(url, callback) {
  request.get({url: url, headers: headers }, callback);
}