What parts does the javascript event consist of

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In javascript, an event consists of an event source, an event type, and an event handler. Event Source refers to the element that triggers the event, Event Type refers to how the event is triggered, and Event Handler refers to the code (in the form of a function) that is executed after the event is triggered.

Operating environment of this tutorial: Windows 7 system, Javascript version 1.8.5, Dell G3 computer.

What is an Event?

Events are actions that can be detected by JavaScript and are a "trigger-response" mechanism. These behaviors refer to specific actions such as page loading, mouse click/double click, mouse pointer sliding in a certain area, etc., which play a very important role in realizing the interactive effect of the page.

Event consists of event source, event type and event handler, which is also called "event three elements."

three elements of event

Event Source: The element that triggers (is) the event

Event type: how the event is triggered (e.g. mouse click or keyboard click)

Event handler: code to execute after an event is triggered (functional form)

The above three elements can be simply understood as "who triggered the event,""what event triggered," and "what to do after triggering the event."

Example: Changing the color of a div by clicking a button

Event Source: Button Element

Event type: mouse click

Event handler: test(eventObj)

mouse events //js How to access the style attribute of an element and make style modifications function test(eventObj) { How do you know if button1 is pressed or button2 is pressed? //window.alert(eventObj.value); if(eventObj.value == "black") { //get div1 var div1 = document.getElementById("div1"); div1.style.background = "black"; } else if(eventObj.value == "red") { var div1 = document.getElementById("div1"); div1.style.background = "red"; } } div1

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