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C # tutorial
HTML DOM allows JavaScript to react to HTML events
A JavaScript can be executed when an event occurs, like when a user clicks on an HTML element.
To execute code when a user clicks on an element, add JavaScript code to an HTML event attribute:
Examples of HTML events:
In this example, the content of the <h1>
element is changed when a user clicks on it:
<!DOCTYPE html>
<html>
<body>
<h1 onclick="this.innerHTML = 'Ooops!'">Click on this text!</h1>
</body>
</html>
In this example, a function is called from the event handler:
<!DOCTYPE html>
<html>
<body>
<h1 onclick="changeText(this)">Click on this text!</h1>
<script>
function changeText(id) {
id.innerHTML = "Ooops!";
}
</script>
</body>
</html>
To assign events to HTML elements you can use event attributes.
Assign an onclick event to a button element:
<button onclick="displayDate()">Try it</button>
In the example above, a function named displayDate
will be executed
when the button is clicked.
The HTML DOM allows you to assign events to HTML elements using JavaScript:
Assign an onclick event to a button element:
<script>
document.getElementById("myBtn").onclick = displayDate;
</script>
In the example above, a function named displayDate
is assigned to
an HTML element with the id="myBtn"
.
The function will be executed when the button is clicked.
The onload
and onunload
events are triggered when the user enters or leaves the page.
The onload
event can be used to check the visitor's browser type and browser version, and load the proper version of the web page based on the information.
The onload
and onunload
events can be used to deal with cookies.
<body onload="checkCookies()">
The onchange
event is often used in combination with validation of input fields.
Below is an example of how to use the onchange. The upperCase()
function will be called when a user changes the content of an input field.
<input type="text" id="fname"
onchange="upperCase()">
The onmouseover
and onmouseout
events can be used to trigger a function when the user mouses
over, or out of, an HTML element:
Mouse Over Me
The onmousedown
, onmouseup
, and onclick
events are all parts of a
mouse-click. First when a mouse-button is clicked, the onmousedown event is
triggered, then, when the mouse-button
is released, the onmouseup event is triggered, finally, when the mouse-click is completed, the onclick event is triggered.
Click Me
For a list of all HTML DOM events, look at our complete HTML DOM Event Object Reference.