DHTML Tutorial

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DHTML Tutorial

Contents Page

DHTML TutorialDHTML IntroDHTML CSSDHTML DOMDHTML EventsDHTML Summary

DHTML DOMDOM Reference

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DHTML is the art of making HTML pages dynamic!

DHTML is a combination of technologies used to create dynamic and interactive Web sites.

To most people DHTML means a combination of HTML, Style Sheets and JavaScript.

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DHTML Tutorial

Introduction to DHTML

What you should already know

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

• HTML • CSS • JavaScript

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

DHTML is NOT a W3C Standard

DHTML stands for Dynamic HTML.

DHTML is not a standard defined by the World Wide Web Consortium (W3C). DHTML is a "marketing term" - used by Netscape and Microsoft to describe the new technologies the 4.x generation browsers would support.

DHTML is a combination of technologies used to create dynamic Web sites.

To most people DHTML means a combination of HTML 4.0, Style Sheets and JavaScript.

W3C once said: "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

With DHTML a Web developer can control how to display and position HTML elements in a browser window.

HTML 4.0

With HTML 4.0 all formatting can be moved out of the HTML document and into a separate style sheet. Because HTML 4.0 separates the presentation of the document from its structure, we have total control of presentation layout without messing up the document content.

Cascading Style Sheets (CSS)

With CSS we have a style and layout model for HTML documents.

CSS was a breakthrough in Web design because it allowed developers to control the style and layout of multiple Web pages all at once. As a Web developer you can define a style for each HTML element and apply it to as many Web pages as you want. To make a global change, simply change the style, and all elements in the Web are updated automatically.

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The Document Object Model (DOM)

DOM stands for the Document Object Model.

The HTML DOM is the Document Object Model for HTML.

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

"The W3C Document Object Model (DOM) is a platform and language neutral interface that allows programs and scripts to dynamically access and update the content, structure, and style of a document".

JavaScript

Allows you to write code to control all HTML elements.

DHTML Technologies in Netscape 4.x and Internet Explorer 4.xNetscape 4.x Cross-Browser DHTML Internet Explorer 4.x

• JSS (JavaScript Style Sheets) (allows you to control how different HTML elements will be displayed)

• Layers (allows you to control element positioning and visibility)

• CSS1 • CSS2 (allows you to control

how different HTML elements will be displayed)

• CSS Positioning (allows you to control element positioning and visibility)

• JavaScript

• Visual Filters (allow you to apply visual effects to text and graphics)

• Dynamic CSS (allows you to control element positioning and visibility)

Note: Problems with coding DHTML technologies WILL occur as long as each browser creates its own proprietary features and technology that is not supported by other browsers. A Web page may look great in one browser and horrible in another.

DHTML CSS Positioning (CSS-P)

CSS is used to style HTML elements.

Examples

Note: Most of the DHTML examples require IE 4.0+, Netscape 7+, or Opera 7+!

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position:relativeHow to position an element relative to its normal position.

position:relativeHow to position all headings relative to their normal position.

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position:absoluteHow to position an element using an absolute value.

Which Attributes can be Used with CSS-P?

First, the element must specify the position attribute (relative or absolute).

Then we can set the following CSS-P attributes:

• left - the element's left position • top - the element's top position • visibility - specifies whether an element should be visible or hidden • z-index - the element's stack order • clip - element clipping • overflow - how overflow contents are handled

Position

The CSS position property allows you to control the positioning of an element in a document.

position:relative

The position:relative property positions an element relative to its current position.

The following example positions the div element 10 pixels to the right from where it's normally positioned:

div{position:relative;left:10;}

position:absolute

The position:absolute property positions an element from the margins of the window.

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The following example positions the div element 10 pixels to the right from the left-margin of its containing block:

div{position:absolute;left:10;}

Visibility

The visibility property determines if an element is visible or not.

visibility:visible

The visibility:visible property makes the element visible.

h1{visibility:visible;}

visibility:hidden

The visibility:hidden property makes the element invisible.

h1{visibility:hidden;}

Z-index

The z-index property is used to place an element "behind" another element. Default z-index is 0. The higher number the higher priority. z-index: -1 has lower priority.

h1{z-index:1;}h2{z-index:2;}

In the example above, if the h1 and h2 elements are positioned on top of each other, the h2 element will be positioned on top of the h1 element.

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Filters

The filter property allows you to add more style effects to your text and images.

h1{width:100%;filter:glow;}

Note: Always specify the width of the element if you want to use the filter property.

The example above produces this output:

Header

Different Filters

Note: Some of the Filter properties will not work unless the background-color property is set to transparent!

Property Argument Description Example

alpha opacityfinishopacitystylestartxstartyfinishxfinishy

Allows you to set the opacity of the element filter:alpha(opacity=20, finishopacity=100, style=1, startx=0, starty=0, finishx=140, finishy=270)

blur adddirectionstrength

Makes the element blur filter:blur(add=true, direction=90, strength=6);

chroma color Makes the specified color transparent filter:chroma(color=#ff0000)

fliph none Flips the element horizontally filter:fliph;

flipv none Flips the element vertically filter:flipv;

glow colorstrength

Makes the element glow filter:glow(color=#ff0000, strength=5);

gray none Renders the element in black and white filter:gray;

invert none Renders the element in its reverse color and brightness values

filter:invert;

mask color Renders the element with the specified background color, and transparent foreground color

filter:mask(color=#ff0000);

shadow colordirection

Renders the element with a shadow filter:shadow(color=#ff0000, direction=90);

dropshadowcolor Renders the element with a dropshadow filter:dropshadow(color=#ff0000,

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offxoffypositive

offx=5, offy=5, positive=true);

wave addfreqlightstrengthphasestrength

Renders the element like a wave filter:wave(add=true, freq=1, lightstrength=3, phase=0, strength=5)

xray none Renders the element in black and white with reverse color and brightness values

filter:xray;

Background

The background property allows you to select your own background.

background-attachment:scroll

The background scrolls along with the rest of the page.

background-attachment:fixed

The background does not move when the rest of the page scrolls.

More Examples

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

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Z-indexZ-index can be used to place an element "behind" another element, using Z-index priority.

Z-indexCheck that the elements now have changed their Z-index priority.

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CursorsChange the style of the mouse cursor with CSS.

FiltersChange the style of your headings using the filter property.

Filters on ImagesThe filter property can also be used on images, here are some filter examples which look good on images.

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WatermarkA background picture that does not move when the rest of the page is scrolling.

DHTML Document Object Model

The Document Object Model gives us access to every element in a document.

Examples

Note: Most of the DHTML examples require IE 4.0+, Netscape 7+, or Opera 7+!

Element accessHow to access an element and change the style.

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

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innerHTMLHow to access and change the innerHTML of an element.

How to access an element?

The element must have an id attribute defined and a scripting language is needed. JavaScript is the most browser compatible scripting language, so we use JavaScript.

<html><body><h1 id="header">My header</h1><script type="text/javascript">document.getElementById('header').style.color="red";</script></body></html>

The script changes the color of the header element, and produces this output.

My header

DHTML Event Handlers

With an event handler you can do something with an element when an event occurs.

Examples

Note: Most of the DHTML examples require IE 4.0+, Netscape 7+, or Opera 7+!

onmouseover & onmouseoutHow to change the color of an element when the cursor moves over and out of an element.

onclickTurn on the light! How you can change an image when you click on it, and back to the original image when you click on it again.

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After clicked over the light….

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onmousedown & onmouseupThis time the light is on only when you hold the mouse button down.

onloadDisplays an alert box when the page has finished loading.

Event handlers

With an event handler you can do something with an element when an event occurs: when the user clicks an element, when the page loads, when a form is submitted, etc.

<h1 onclick="style.color='red'">Click on this text</h1>

The example above defines a header that turns red when a user clicks on it.

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

<html><head><script type="text/javascript">function changecolor()

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{document.getElementById('header').style.color="red";}</script></head><body><h1 id="header" onclick="changecolor()">Click on this text</h1></body></html>

HTML 4.0 Event HandlersEvent Occurs when...

onabort a user aborts page loading

onblur a user leaves an object

onchange a user changes the value of an object

onclick a user clicks on an object

ondblclick a user double-clicks on an object

onfocus a user makes an object active

onkeydown a keyboard key is on its way down

onkeypress a keyboard key is pressed

onkeyup a keyboard key is released

onloada page is finished loading. Note: In Netscape this event occurs during the loading of a page!

onmousedown a user presses a mouse-button

onmousemove a cursor moves on an object

onmouseover a cursor moves over an object

onmouseout a cursor moves off an object

onmouseup a user releases a mouse-button

onreset a user resets a form

onselect a user selects content on a page

onsubmit a user submits a form

onunload a user closes a page

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You Have Learned DHTML, Now What?

DHTML Summary

This tutorial has taught you how to use DHTML to create more dynamic and interactive Web sites.

You have learned how to use the combination of HTML, CSS and JavaScript to animate HTML documents.

For more information on DHTML, please look at our DHTML examples and our DHTML reference.

Now You Know DHTML, What's Next?

The next step is to learn about the HTML DOM and ASP.

HTML DOM

The HTML DOM defines a standard way for accessing and manipulating HTML documents.

The HTML DOM is platform and language independent and can be used by any programming language like Java, JavaScript, and VBScript.

If you want to learn more about the DOM, please visit our HTML DOM tutorial.

ASP

While scripts in an HTML file are executed on the client (in the browser), scripts in an ASP file are executed on the server.

With ASP you can dynamically edit, change or add any content of a Web page, respond to data submitted from HTML forms, access any data or databases and return the results to a browser, customize a Web page to make it more useful for individual users.

Since ASP files are returned as plain HTML, they can be viewed in any browser.

If you want to learn more about ASP, please visit our ASP tutorial.

DHTML DOM Objects

With JavaScript you can access and manipulate all of the HTML DOM objects.

HTML DOM Objects

The HTML DOM is a W3C standard and it is an abbreviation for the Document Object Model for HTML.

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

All HTML elements, along with their containing text and attributes, can be accessed through the DOM. The contents can be modified or deleted, and new elements can be created.

The HTML DOM is platform and language independent. It can be used by any programming language like Java, JavaScript, and VBScript.

Follow the links below to learn more about how to access and manipulate each DOM object with JavaScript:

Object Description

Anchor Represents an HTML a element (a hyperlink)

Applet Represents an HTML applet element. The applet element is used to place executable content on a page

Area Represents an area of an image-map. An image-map is an image with clickable regions

Base Represents an HTML base element

Basefont Represents an HTML basefont element

Body Represents the body of the document (the HTML body)

Button Represents a push button on an HTML form. For each instance of an HTML <input type="button"> tag on an HTML form, a Button object is created

Checkbox Represents a checkbox on an HTML form. For each instance of an HTML <input type="checkbox"> tag on an HTML form, a Checkbox object is created

Document Used to access all elements in a page

Event Represents the state of an event, such as the element in which the event occurred, the state of the keyboard keys, the location of the mouse, and the state of the mouse buttons

FileUpload For each instance of an HTML <input type="file"> tag on a form, a FileUpload object is created

Form Forms are used to prompt users for input. Represents an HTML form element

Frame Represents an HTML frame

Frameset Represents an HTML frameset

Hidden Represents a hidden field on an HTML form. For each instance of an HTML <input type="hidden"> tag on a form, a Hidden object is created

History A predefined object which can be accessed through the history property of the Window object. This object consists of an array of URLs. These URLs are all the URLs the user has visited within a browser window

Iframe Represents an HTML inline-frame

Image Represents an HTML img element

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Link Represents an HTML link element. The link element can only be used within the <head> tag

Location Contains information about the current URL

Meta Represents an HTML meta element

Navigator Contains information about the client browser

Option Represents an option in a selection list on an HTML form. For each instance of an HTML <option> tag in a selection list on a form, an Option object is created

Password Represents a password field on an HTML form. For each instance of an HTML <input type="password"> tag on a form, a Password object is created

Radio Represents radio buttons on an HTML form. For each instance of an HTML <input type="radio"> tag on a form, a Radio object is created

Reset Represents a reset button on an HTML form. For each instance of an HTML <input type="reset"> tag on a form, a Reset object is created

Screen Automatically created by the JavaScript runtime engine and it contains information about the client's display screen

Select Represents a selection list on an HTML form. For each instance of an HTML <select> tag on a form, a Select object is created

Style Represents an individual style statement. This object can be accessed from the document or from the elements to which that style is applied

Submit Represents a submit button on an HTML form. For each instance of an HTML <input type="submit"> tag on a form, a Submit object is created

Table Represents an HTML table element

TableData Represents an HTML td element

TableHeader Represents an HTML th element

TableRow Represents an HTML tr element

Text Represents a text field on an HTML form. For each instance of an HTML <input type="text"> tag on a form, a Text object is created

Textarea Represents an HTML textarea element

Window Corresponds to the browser window. A Window object is created automatically with every instance of a <body> or <frameset> tag

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