Reopening same window again in selenium WebdriverJs

I am really new to this selenium , I managed to open a website using below nodejs code

var webdriver = require('selenium-webdriver');

var driver = new webdriver.Builder()
    .forBrowser('chrome')
    .build();
console.log(driver);

driver.get('https://web.whatsapp.com');

var cookies = driver.manage().getCookies(); 

now https://web.whatsapp.com is opened and I manually scan QR code and log in.Now I have different javascript files to perform actions as delete , clear chat inside web.whatsapp.com etc...

Now I need to use the same session I have logged in above.So basically , right now each time I run new script it opens new browser window and I gotta scan QR code each time .But instead how to reopen same browser window where my whatsapp is logged in and my script continues to work on it.

via Vishnu