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    8                                 Introduction to

                                                             Event Handling

                         Let’s surf
                             What is Event and Event Handling                Examples of Events
                             Onclick Event                                   Using Functions for Event Handling

                     The way  that JavaScript interacts  with  HTML  is  through  events that  happen  whenever a  user
                     or browser modifies a page. The actions of pressing any key/button, closing a window, resizing a
                     window, etc. are examples of events.

                            WHAT IS EVENT AND EVENT HANDLING

                     An event is defined as a change in an object's state. There are a number of events in HTML that show
                     when a user or browser performs a certain action. JavaScript responds to these events when JS code
                     is embedded in HTML and permits execution. The act of responding to events is known as event
                     handling. As a result, JavaScript uses event handlers to handle HTML events.

                            EXAMPLES OF EVENTS

                     There are various types of events that can occur. For example:
                     •  On a certain element, the user performs selection, clicking, or hovering of the cursor.

                     •  The user clicks a key on the keyboard.
                     •  Resizing or closing the browser window.

                     •  A web page completes loading.                                            Tech Fact

                     •  Submission of a form.                                       Event handlers are also referred
                     •  A video plays, is paused, or ended.                         to as event listeners.

                     •  An error takes place
                     You can attach an event handler to an event to respond to it. This is a section of code that executes
                     when the event occurs, often a JavaScript function that you write as a programmer. We refer to
                     defining such a section of code to execute in response to an event as "registering an event handler."

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