How to start TwitterOAuth with Express.js

What kind of procedure OAuth process in Twitter?
If you want tweet with OAuth flow,You must get Access token and access token secret.

twitterOAuth flow

Preparation

Getting oauth_consumer_key,oauth_consumer_secret, and setting oauth_callback in Twitter Developers.

• oauth_consumer_key(=API Key)
• oauth_consumer_secret(=API Key Secret)
• oauth_callback:without this URL,error in OAuth flow.

1. POST to oauth/request_token

After POST to oauth/request_token with oauth_consumer_key and oauth_callback,you'll get this.

• oauth_token(=request token)
• oauth_token_secret(=request token secret)
• oauth_callback_confirmed.

2. GET to oauth/authorize

redirect to your setting callback_url containing the oauth_token and oauth_verifier.

3. POST oauth/access_token

post to oauth/access_token includes oauth_consumer_key,oauth_token(=request token),and oauth_verifier.
So,you can receive oauth_token(=access token) and oauth_token_secret(=access token secret).

After saved this,use twitter client library.

fucntion twitterPost(consumerKey,consumerSecret,AccessTokenKey,AccessTokenSecret){
  const Twitter = require('twitter');
  const client = new Twitter({
    consumer_key: consumerKey,
    consumer_secret: consumerSecret,
    access_token_key: AccessTokenKey,
    access_token_secret: AccessTokenSecret
  });
}

TwitterOAuth with express

using this

• express
• express-session
• node-twitter-api

Preparation

loading environment variables from a .env file

const consumerKey = process.env.CONSUMER_KEY;
const consumerSecret = process.env.CONSUMER_SECRET;
const callbackURL = process.env.CALLBACK_URL;

setting session.

app.use(
  session({
    secret: "keyboard cat",
    resave: true,
    saveUninitialized: false,

    cookie: { secure: false,},
    key: "sid",
  })
);

Saving to session oauth_token(=requestToken) and oauth_token_secret(=requestTokenSecret).
GET oauth/authenticate after that.

const twitterAPI = require("node-twitter-api");

const twitterapi = new twitterAPI({
  consumerKey: consumerKey,
  consumerSecret: consumerSecret,
  callback: callbackURL,
});

router.get("/", (req, res) => {
  const sess = req.session;
  twitter.getRequestToken(function (
    error,
    requestToken,
    requestTokenSecret,
  ) {
    if (error) {
      console.log("Error getting OAuth request token : " + error);
    } else {
      sess.requestToken = requestToken;

      sess.requestTokenSecret = requestTokenSecret;
      res.redirect(
        `https://twitter.com/oauth/authenticate?oauth_token=${requestToken}`
      );
    }
  });
});

after verify your app,redirect your setting callback_url.check request_token.

router.get("/callback", (req, res) => {
  const sess = req.session;
  const requestTokenSecret = sess.requestTokenSecret;
  const oauth_token = req.query.oauth_token;
  const oauth_verifier = req.query.oauth_verifier;

  twitter.getAccessToken(
    oauth_token,
    requestTokenSecret,
    oauth_verifier,
    function (error, accessToken, accessTokenSecret) {
      if (error) {
        console.log("access token error!");
        console.log(error);
      } else {
        sess.token = accessToken;
        sess.tokenSecret = accessTokenSecret;
        res.redirect("/twitterPost");
      }
    }
  );
});

app.get("/twitterPost", (req, res) => {
  const sess = req.session;
  twitterPost(
    consumerKey,
    consumerSecret,
    sess.token,
    sess.tokenSecret,
  );
  res.send(
    `your tweet was posted!`
  );
});