Events in JavaScript

→Traditional English grammar:

• Infinitive events (like: do): At the start of event it's triggered.
• Past participle events (like: done): On the completion of event it's triggered. 

→Types of Events

• When click on mouse or drag.
• When press any keyboard key.
• Automatically run events after specific program/function execution.

→Event

• Suppose when you click on a mouse then an event occur. It doesn't mean only one function or procedure execute for events. May be group of programs run for specific events.

→preventDefault() functionality:

• All infinitive events provide preventDefault() functionality. 
• Can stop the execution of an action before it starts. 
• Return false when called [return e.preventDefault()].

Ref:https://getbootstrap.com/docs/4.1/getting-started/javascript/