[JavaScript] JavaScript learning sixteen JavaScript events

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• Event example:

Events are behaviors that can be detected by JavaScript.

Event

Javascript enables us to create dynamic pages. Events are behaviors that can be detected by JavaScript.

Each element in the web page can generate events that can trigger JavaScript Functions. For example, when a user clicks a button, an onclick event is generated to trigger a function. Events are defined on the HTML page.

Event example:

• Click
• Page or image loading
• Hover your mouse over a hotspot on the page
• Select input box in the form
• Confirmation Form
• Keyboard buttons

Note: events are usually used with functions. when an event occurs, the function is executed.

If you need more JavaScript Event Identification knowledge, read our JavaScript event reference manual.

Onload and onUnload

When a user enters or leaves the page, the onload and onUnload events are triggered.

The onload event is often used to detect the browser type and version of a visitor, and then load the webpage of a specific version based on the information.

Onload and onUnload events are often used to process cookies created when users enter or exit the page. For example, when a user first enters the page, you can use a message box to ask the user's name. The name is saved in the cookie. When the user enters this page again, you can use another message box to greet the user: "Welcome John Doe! ".

Onfocus, onblur and onchange

Onfocus, onblur, and onchange events are usually used together to verify the form.

The following is an example of using the onchange event. Once the user changes the domain content, the checkemail () function will be called.

<input type="text" size="30" id="email" onchange="checkEmail()">

Onsubmit

Onsubmit is used to verify all form fields before submitting a form.

The following is an example of using the onsubmit event. When you click the OK button in the form, the checkform () function is called. If the field value is invalid, this submission will be canceled. The Return Value of the checkform () function is true or false. If the return value is true, the form is submitted, and vice versa.

<form method="post" action="xxx.htm" onsubmit="return checkForm()">

Onmouseover and onmouseout

Onmouseover and onmouseout are used to create "dynamic" buttons.

The following is an example of using the onmouseover event. When the onmouseover event is detected by the script, a warning box is displayed:

<a href="http://www.w3school.com.cn"onmouseover="alert('An onMouseOver event');return false"></a>