DHTML Tutorial

DHTML is NOT a language.

DHTML is a TERM describing the art of making dynamic and interactive web pages.

DHTML combines HTML, JavaScript, DOM, and CSS.

Start learning DHTML now!

Introduction to DHTML

DHTML is the art of combining HTML, JavaScript, DOM, and CSS.

What you should already know

Before you continue you should have a basic understanding of the following:

HTML

JavaScript

CSS

If you want to study these subjects first, find the tutorials on our Home Page.

DHTML is Not a Language

DHTML stands for Dynamic HTML.

DHTML is NOT a language or a web standard.

DHTML is a TERM used to describe the technologies used to make web pages dynamic and interactive.

To most people DHTML means the combination of HTML, JavaScript, DOM, and CSS.

According to the World Wide Web Consortium (W3C):"Dynamic HTML is a term used by some vendors to describe the combination of HTML, style sheets and scripts that allows documents to be animated."

DHTML Technologies

Below is a listing of DHTML technologies.

HTML 4

The W3C HTML 4 standard has rich support for dynamic content:

HTML supports JavaScript

HTML supports the Document Object Model (DOM)

HTML supports HTML Events

HTML supports Cascading Style Sheets (CSS)

DHTML is about using these features to create dynamic and interactive web pages.

JavaScript

JavaScript is the scripting standard for HTML.

DHTML is about using JavaScript to control, access and manipulate HTML elements.

You can read more about this in the next chapter of this tutorial.

HTML DOM

The HTML DOM is the W3C standard Document Object Model for HTML.

The HTML DOM defines a standard set of objects for HTML, and a standard way to access and manipulate them.

DHTML is about using the DOM to access and manipulate HTML elements.

You can read more about this in a later chapter of this tutorial.

HTML Events

The W3C HTML Event Model is a part of the HTML DOM.

It defines a standard way to handle HTML events.

DHTML is about creating web pages that reacts to (user)events.

You can read more about this in a later chapter of this tutorial.

CSS

CSS is the W3C standard style and layout model for HTML.

CSS allows web developers to control the style and layout of web pages.

HTML 4 allows dynamic changes to CSS.

DHTML is about using JavaScript and DOM to change the style and positioning of HTML elements.

You can read more about this in a later chapter of this tutorial.

DHTML JavaScript

JavaScript can create dynamic HTML content:

Date: Sat Oct 25 14:44:49 2008

JavaScript Alone

If you have studied JavaScript, you already know that the statement:

document.write()can be used to display dynamic content to a web page.

ExampleUsing JavaScript to display the current date:

document.write(Date());

Try it Yourself

JavaScript and the HTML DOM

With HTML 4, JavaScript can also be used to change the inner content and attributes of HTML elements dynamically.

To change the content of an HTML element use:

document.getElementById(id).innerHTML=new HTMLTo change the attribute of an HTML element use:

document.getElementById(id).attribute=new valueYou will learn more about JavaScript and the HTML DOM in the next chapter of this tutorial.

JavaScript and HTML Events

New to HTML 4 is the ability to let HTML events trigger actions in the browser, like starting a JavaScript when a user clicks on an HTML element.

To execute code when a user clicks on an element, use the following event attribute:

onclick=JavaScriptYou will learn more about JavaScript and HTML Events in a later chapter.

JavaScript and CSS

With HTML 4, JavaScript can also be used to change the style of HTML elements.

To change the style of an HTML element use:

document.getElementById(id).style.property=new styleYou will learn more about JavaScript and CSS in a later chapter of this tutorial.

DHTML - HTML Document Object Model (DOM)

The DOM presents HTML as a tree-structure (a node tree), with elements, attributes, and text:

Examples

innerHTMLHow to access and change the innerHTML of an element.

Attribute changeHow to access an image element and change the "src" attribute.

What is the HTML DOM?

The HTML DOM is:

A standard object model for HTML

A standard programming interface for HTML

Platform- and language-independent

A W3C standard

The HTML DOM defines the objects and properties of all HTML elements, and the methods (interface) to access them.

In other words:

The HTML DOM is a standard for how to get, change, add, or delete HTML elements.

Using the HTML DOM to Change an HTML Element

The HTML DOM can be used to change the content of an HTML element:

Old Header

document.getElementById("header").innerHTML="New Header";

HTML output:

New Header

Example explained:

The HTML document contains a header with id="header"

The DOM is used to get the element with id="header"

A JavaScript is used to change the HTML content (innerHTML)

Try it yourself

Using the HTML DOM to Change an HTML Attribute

The HTML DOM can be used to change the attribute of an HTML element:

document.getElementById("image").src="landscape.jpg";

HTML output:

DHTML Event Handlers

HTML events can trigger actions in the browser, like starting a JavaScript when a user clicks on an element.

Don't Click On This Text

Examples

onclickTurn on the light! How to change an image when the user clicks it.

onmousedown & onmouseupThis time the light is on only when the user holds down the mouse button.

onloadDisplays an alert box when the page has finished loading.

Event handlers

An event handler allows you to execute code when an event occurs.

Events are generated by the browser when the user clicks an element, when the page loads, when a form is submitted, etc.

ExampleA header changes when the user clicks it:

Click on this text

Try it yourselfYou can also add a script in the head section of the page and then call the function from the event handler:

function changetext(id)

{

id.innerHTML="Ooops!";

}

Click on this text

HTML 4.0 Event Handlers

EventOccurs when...

onaborta user aborts page loading

onblura user leaves an object

onchangea user changes the value of an object

onclicka user clicks on an object

ondblclicka user double-clicks on an object

onfocusa user makes an object active

onkeydowna keyboard key is on its way down

onkeypressa keyboard key is pressed

onkeyupa keyboard key is released

onloada page is finished loading

onmousedowna user presses a mouse-button

onmousemovea cursor moves on an object

onmouseovera cursor moves over an object

onmouseouta cursor moves off an object

onmouseupa user releases a mouse-button

onreseta user resets a form

onselecta user selects content on a page

onsubmita user submits a form

onunloada user closes a page

More About HTML Events

For a full overview please refer to the complete DOM Event Object Reference in our HTML DOM tutorial.

DHTML CSS

JavaScript can be used to change the style an HTML element:

Examples

Change the style of the current elementHow to change the style of an element using the this object.

Change the style of a specific elementHow to change the style of an element using getElementById.

(You can find more examples at the bottom of this page)

JavaScript, DOM, and CSS

With HTML 4, JavaScript and the HTML DOM can be used to change the style any HTML element.

To change the style the current HTML element, use the statement:

style.property=new styleor more correctly:

this.style.property=new styleTry it yourselfTo change the style of a specific HTML element, use the statement:

document.getElementById(element_id).style.property=new styleTry it yourself

More examples

Mouse EventsHow to change the color of an element when the cursor moves over it.

VisibilityHow to make an element invisible. Do you want the element to show or not?

More About JavaScript, DOM, And CSS

For a full overview please refer to the complete DOM Style Object Reference in our HTML DOM tutorial.

To learn more about CSS, find the complete CSS tutorial on our Home Page.

1.

h1.ex1

{

position:relative;

left:20px;

}

h1.ex2

{

position:relative;

left:-20px;

}

Normal Heading

Heading +20

Heading -20

Relative positioning moves an element relative to its original position.

"left:20" adds 20 pixels to the element's LEFT position.

"left:-20" subtracts 20 pixels from the element's LEFT position.

2.

h1

{

position:relative;

left:40px;

}

Heading A

This is a paragraph.

Heading B

This is a paragraph.

Heading C

This is a paragraph.

Heading D

This is a paragraph.

3.

h1.x

{

position:absolute;

left:100px;

top:150px;

}

This is a heading

With absolute positioning, an element can be placed anywhere on a page.

The LEFT position of the heading is 100 pixels from the left of the page.

The TOP position is 150 pixels from the top of the page.

4.

In my younger and more vulnerable years my father gave me some advice that I've been turning over in my mind ever since.

'Whenever you feel like criticizing anyone,' he told me, just remember that all the people in this world haven't had the advantages that you've had.'

5.

img.x

{

position:absolute;

left:0px;

top:0px;

z-index:-1;

}

This is a Heading

Default z-index is 0. Z-index -1 has lower priority.

6.

img.x

{

position:absolute;

left:0px;

top:0px;

z-index:1;

}

This is a Heading

Default z-index is 0. Z-index 1 has higher priority.

7.

Move the mouse over the words to see the cursor change

Auto

Crosshair

Default

Pointer

Move

e-resize

ne-resize

nw-resize

n-resize

se-resize

sw-resize

s-resize

w-resize

text

wait

help

8.

body

{

background-attachment: fixed;

background-image: url("bulboff.gif");

background-repeat: no-repeat;

}

Scroll the page and see what happens

Scroll the page and see what happens

Scroll the page and see what happens

Scroll the page and see what happens

Scroll the page and see what happens

Scroll the page and see what happens

Scroll the page and see what happens

Scroll the page and see what happens

Scroll the page and see what happens

9.

function bgChange(bg)

{

document.body.style.background=bg;

}

Mouse over the squares and the background color will change!

10.

function mymessage()

{

alert("This message was triggered from the onload event");

}

11

function mymessage()

{

alert("This message was triggered from the onunload event");

}

An alert box will display a message when you close this document!

13

function preferedBrowser()

{

prefer=document.forms[0].browsers.value;

alert("You prefer browsing internet with " + prefer);

}

Choose which browser you prefer:

Internet Explorer

Netscape

14

function confirmInput()

{

fname=document.forms[0].fname.value;

alert("Hello " + fname + "! You will now be redirected to www.w3Schools.com");

}

Enter your name:

15

function message()

{

alert("This alert box was triggered by the onreset event handler");

}

Enter your name:

16

function message()

{

alert("This alert box was triggered by the onblur event handler");

}

The onblur event occurs when an element loses focus. Try to click or write in the input field below, then click elsewhere in the document so the input field loses focus.

Enter your name:

17

function message()

{

alert("This alert box was triggered by the onfocus event handler");

}

Enter your name:

18

function writeMessage()

{

document.forms[0].mySecondInput.value=document.forms[0].myInput.value;

}

The onkeydown event occurs when the a keyboard key is on it's way DOWN.

Enter your name:

19

function writeMessage()

{

document.forms[0].mySecondInput.value=document.forms[0].myInput.value;

}

The onkeyup event occurs when the a keyboard key is on it's way UP.

Write a message:

20

Click Me!

If you click the header above, it turns red.

21

document.getElementById("image").src="landscape.jpg";

The original image was smiley.gif, but the script changed it to landscape.jpg

22

txtsize=0;

maxsize=100;

function writemsg()

{

if (txtsize