Working with Javascript timing alerts using explicit wait is demonstrated in this video.
We use IntelliJ IDEA, Maven, Java, TestNG, WebDriverManager and Selenium WebDriver in this video.
Prerequisites : It is assumed that you are already familiar with launching a browse, clikcing button and extracting visible text from an element
Further reading :
https://pragmatictestlabs.com/2018/02/12/working-javascript-popup-boxes-selenium-webdriver/
Pragmatic Training
https://pragmatictestlabs.com/training/