How to Automate OAuth2 Token Renewal in Postman

pre-request.js

// ###########################################################################
// Define required packages
// ###########################################################################

let moment = require("moment"); // Used to create/format date

// ###########################################################################
// Define variables
// ###########################################################################

let AUTH              = pm.environment.get("AUTH"); // Get current JWT token value
let AUTH_CREATED_DATE = pm.environment.get("AUTH_CREATED_DATE"); // Get JWT token creation date
let AUTH_EXPIRES_IN   = pm.environment.get("AUTH_EXPIRES_IN"); // Get JWT token expiration time (in seconds)
let AUTH_TYPE         = pm.environment.get("AUTH_TYPE"); // Get JWT token type (e.g. Bearer)
let NOW               = moment(); // Create a new datetime
let AUTH_EXPIRED_DATE; // Define this variable for the expiration calculation

let AUTH_CLIENT_ID    = pm.environment.get("AUTH_CLIENT_ID") // Get JWT token client ID
let AUTH_USERNAME     = pm.environment.get("AUTH_USERNAME"); // Get JWT token username
let AUTH_PASSWORD     = pm.environment.get("AUTH_PASSWORD"); // Get JWT token password

// ###########################################################################
// Check if there is any environment variable empty or undefined
// ###########################################################################

if (!AUTH_CREATED_DATE || !AUTH_TYPE || !AUTH_EXPIRES_IN || !AUTH) {
    AUTH_EXPIRED_DATE = NOW;
} else {
    AUTH_EXPIRED_DATE = moment(new Date(AUTH_CREATED_DATE)).add(AUTH_EXPIRES_IN, 'seconds');
}

// ###########################################################################
// Generate Token
// ###########################################################################

if(AUTH_EXPIRED_DATE <= NOW) {
    console.info("Updating JWT Token... wait!");
    pm.sendRequest({
        url: "PUT_YOUR_URL_HERE", 
        method: "POST",
        header: {
            "Content-Type": "application/x-www-form-urlencoded"
        },
        body: {
            mode: "urlencoded",
            urlencoded: [
                {key: "username", value: `${AUTH_USERNAME}`, disabled: false},
                {key: "password", value: `${AUTH_PASSWORD}`, disabled: false},
                {key: "grant_type", value: "password", disabled: false},
                {key: "client_id", value: `${AUTH_CLIENT_ID}`, disabled: false},
                {key: "response_type", value: "token id_token", disabled: false},
                {key: "scope", value: `openid ${AUTH_CLIENT_ID} offline_access`, disabled: false},
            ] 
        }
        }, function (error, response) {
            if (error !== null) {
                console.error(error);
            } else {
                pm.environment.set("AUTH", response.json().access_token);
                pm.environment.set("AUTH_TYPE", response.json().token_type);
                pm.environment.set("AUTH_CREATED_DATE", response.headers.get("Date"))
                pm.environment.set("AUTH_EXPIRES_IN", response.json().expires_in);
                console.info("The AUTH environment was updated");

                pm.test('The AUTH TOKEN was created', function() {
                    pm.expect(response.code).to.be.equal(200);
                });
            }
    });
}