How to integrate OKTA SAML with NodeJS or AngularJS - node.js

Question

I have a Web Application using NodeJS + AngularJS, I want to integrate OKTA SAML with my application(Using Okta as IdP, using our Application as SP), right now I have some info after configuration on Okta End, it like this:
https://www.pastepic.xyz/image/image.abqL4
https://www.pastepic.xyz/image/image.ab3G3
I have Idp Single-Sign On URL, IdP Issuer, X.509 Certificate and also MetaData.
My question is how to integrate it with NodeJS oR AngularJS, How should I use the data from okta.
I have tried to use passport library in NodeJS, the app.js like this:
var express = require("express");
var path = require("path");
var bodyParser = require("body-parser");
var routes = require("./api/routes");
var http = require("http");
var morgan = require('morgan');
var cookieParser = require('cookie-parser');
var session = require('express-session');
var passport = require('passport');
require("./api/helper/global_function");
// Defining the port and env to run on
const { environment, port, samlUrl } = require('./appconfig.js');
const PORT = port || 8000;
const ENV = environment || 'dev'
const SAMLURL = samlUrl
const config = require('./api/auth/config.js')[ENV];
require('./api/auth/passport.js')(passport, config);
var app = express();
app.set("port", PORT);
app.set("env", ENV)
app.set("samlUrl", SAMLURL)
// To Allow CORS calls
app.use(function (req, res, next) {
res.header('Access-Control-Allow-Origin', '*')
res.header('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE');
res.header('Access-Control-Allow-Headers', 'Content-Type, Authorization');
res.header('Access-Control-Allow-Credentials', true);
return next();
});
app.use(morgan('combined'));
app.use(cookieParser());
app.use(session(
{
resave: true,
saveUninitialized: true,
secret: 'something'
}));
// Enable parsing of posted forms
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(passport.initialize());
app.use(passport.session());
// Set static directory before defining routes
app.use(express.static(path.join(__dirname, "dist")));
app.use("/node_modules", express.static(__dirname + "/node_modules"));
// Add some routing
app.use("/", function (req, res, next) {
if (req.isAuthenticated()) {
console.log(req.isAuthenticated())
return next();
}
req.session.returnTo = req.originalUrl;
res.redirect(samlUrl);
});
app.use("/api", routes);
app.use("*", (req, res) => {
res.sendFile(path.join(__dirname, 'dist/index.html'));
});
// To verify the listen is up and running
var server = app.listen(app.get("port"), function () {
var port = server.address().port;
console.log("Magic happens on port " + port);
});
It doesn't work because all request is unauthenticated, when I make a api call, the application keep directing me to single sign on page.
Maybe I am absolutely wrong about this, can somebody help me out? Give me a hint or tell me some basic logic
Can any people help with SAML? If any unclear, please add a comment or answer, I will check in a very short time.