For example, use it in form validation for showing the warning on invalid input or using it to display the alert message when form successfully submitted. There are many other cases when you can use this.
But, the problem is it does not look good on the screen.
There are many free jQuery plugins that you can use to show the user-friendly message box.
In this tutorial, I am using sweetAlert jQuery plugin to show custom message box on the screen and use it as an alternative to default alert box.
It looks much better than default alert and it is responsive.