How to handle JS Alerts in Playwright?

 What are JS Alerts ?

An alert box is often used if you want to make sure information comes through to the user.

JavaScript has three kind of popup boxes: 

• Alert box, 

• Confirm box, and 

• Prompt box. 

alert(), confirm(), prompt() dialogs​

By default, dialogs are auto-dismissed by Playwright, so you don't have to handle them. However, you can register a dialog handler before the action that triggers the dialog to either Dialog.accept() or Dialog.dismiss() it.

page.onDialog(dialog -> System.out.println(dialog.message()));

Note : 
If there is no listener for Page.onDialog(handler), all dialogs are automatically dismissed.

For Prompt alert we need handle explicitly write page listener onDialog methods
 page.onDialog(dialog -> {
            System.out.println(dialog.message());
            //dialog.accept("Accepting with Entered data");
            dialog.type();          
            dialog.dismiss();
            //dialog.accept("Accepting with Entered data");
        });

Example web sites : 

https://www.lambdatest.com/selenium-playground/javascript-alert-box-demo

https://www.lambdatest.com/selenium-playground/javascript-alert-box-demo

Sample Program as below 

package com.example;

import com.microsoft.playwright.Browser;
import com.microsoft.playwright.BrowserType;
import com.microsoft.playwright.Page;
import com.microsoft.playwright.Playwright;

public class Alerts2Example {

    public static void main(String[] args) {
        Playwright playwright = Playwright.create()  ;
        Browser browser = playwright.chromium().launch(new BrowserType.LaunchOptions()
                .setHeadless(false)
                .setChannel("chrome"));
        Page page = browser.newPage();
       // page.navigate("https://web-scraping.dev/product/1?variant=orange-small");
      //  page.locator("//button[contains(@class,'btn btn-secondary')]").click();
      //  page.locator(".cart-icon").click();
      //  page.locator("//button[normalize-space(text())='Clear']").click();
        page.navigate("https://www.lambdatest.com/selenium-playground/javascript-alert-box-demo");
       // page.locator("(//button[contains(@class,'btn btn-dark')])[1]").click();
        page.onDialog(dialog -> {
            System.out.println(dialog.message());
            //dialog.accept("Accepting with Entered data");
            dialog.type();
            dialog.dismiss();
            //dialog.accept("Accepting with Entered data");
        });
       page.locator("(//button[contains(@class,'btn btn-dark')])[2]").click();
      //  page.locator("(//button[contains(@class,'btn btn-dark')])[3]").click();

    }
}