CODEWITHSUNDEEP
node.jspassport.js
Alwaysblue
Alwaysblue

Reputation: 11880

How Passport Strategy works behind the Scene

I was trying to comprehend how passport strategy is working.

Consider these api routes which I am using to authenticate.

  router.get("/google",  passport.authenticate('google', { scope: ['profile', 'email'] }));
  router.get("/google/callback", passport.authenticate('google'), (req, res) => {
      res.redirect("http://localhost:3000/")
  })

And this is the passport strategy

const passport = require('passport')
const GoogleStratergy = require('passport-google-oauth20')
const keys = require("./key.js")
const User = require("../models/user-model.js")

passport.serializeUser((user, done) => {
    done(null, user.id) 
})

passport.deserializeUser((id, done) => {
    User.findById(id).then((user) => {
        done(null, user) //pass it in req of our routes
    })
})

passport.use(
    new GoogleStratergy({
    //Options for the stratergy 
        callbackURL: "/auth/google/callback", 
        clientID: keys.google.clientID,
        clientSecret: keys.google.clientSecret
    }, (accessToken, refreshToken, profile, done) => {


        User.findOne({userId: profile.id }).then((currentUser) => {
            if (currentUser) {
                done(null, currentUser)
            } else {
                    //Changing Image String
                    let  oldURL=  profile.photos[0]["value"]
                    let newURL =  oldURL.substr(0,  oldURL.length-2);
                    newURL = newURL + "250"
                //Creating Mongoose Database
                    new User({
                        username: profile.displayName,
                        userId: profile.id,
                        image: newURL,
                        email: profile.emails[0]["value"]
                    }).save().then((newUser) => {
                        console.log("new user created", newUser)
                        done(null, newUser)
                   })
            }

        })

    })
)

Now, I think I understand what is happening here, but one thing I am unable to comprehend here is..

How is 

passport.use(
    new GoogleStratergy({
    //Options for the stratergy

being called here? I mean I don't see any export statements, so how is it linked with out Node App? or how does passport knows behind the scene about the location of our google strategy **

Also, Just to confirm, after we pass done from our passport.use? it goes to serialize?

Upvotes: 4

Views: 746

Answers (1)

Vasan
Vasan

Reputation: 4956

When you require passport, you get a singleton instance i.e. it's constructed the first time you require passport, and is reused every time and everywhere it's required subsequently.

So you don't need to share the instance between modules i.e. no need for export. Any configuration you do on the instance is visible everywhere you require it.

There are other objects in NodeJS that work the same way, one prominent example is the express app instance.

Here is the source code for passport where you can verify this.

Upvotes: 5

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