1 Introduction to Web Application Implement JavaScript in HTML.

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Introduction to Web Application

Implement JavaScript in HTML

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References

• http://10.89.115.100:8086/material/JavaScriptBibleGoldEn.pdf

• Web Development/HTML and Dynamic HTML/DHTML Reference

• http://www.w3.org/DOM

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Introduction• Dynamic HTML Object Model

– Allows Web authors to control the presentation of their pages

– Gives them access to all the elements on their pages

• Web page– Elements, forms, frames, tables

– Represented in an object hierarchy

• Scripting– Retrieve and modify properties and attributes

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Object Referencing• The simplest way to reference an element is by

using the element’s id attribute.• The element is represented as an object

– HTML attributes become properties that can be manipulated by scripting

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Example of all<html> <head> <title>Object Model</title> <script type = "text/javascript">  </script>

</head> <body onload = "start()"> <p id = "pText">Welcome to our Web page!</p> </body></html>

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Collections all and children• Collections

– Arrays of related objects on a page

– all• all the HTML elements in a document

– children• Specific element contains that element’s child elements

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<html> <head> <title>Object Model</title> <script type = "text/javascript">  </script> </head>

<body onload = "start()"> <p id = "pText">Elements on this Web page:</p> </body></html>

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<html> <head> <title>Object Model</title> <script type = "text/javascript">  </script> </head>

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<body onload = "child( document.all[ 4 ] );

myDisplay.outerHTML += elements;

myDisplay.outerHTML += '</ul>';">

<p>Welcome to our <strong>Web</strong> page!</p>

<p id = "myDisplay">

Elements on this Web page:

</p> </body>

</html>

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The Document Object Model

• The DOM is an abstract model that defines the interface between HTML documents and application programs

• Documents in DOM have a tree-like structure

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The Document Object Model• Under development by w3c since the mid-90s• DOM is a successor to DHTML• DOM now has 4 levels• DOM0 is designed to deal with just HTML

documents• DOM1 is focused on the HTML and XML

document model, all modern browser has supported DOM1– Appendix

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• DOM 2 is the latest approved standard, which specifies a CSS object model and include document traversals and an event model, but none modern browser can fully support DOM2

• DOM3 is under development

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The Document Object Model• It is an OO model - document elements are

objects• A language that supports the DOM must

have a binding to the DOM constructs• In the JavaScript binding, HTML elements

are represented as objects and element attributes are represented as properties– e.g., <input type = "text" name = "address">

would be represented as an object with two properties, type and name, with the values "text" and "address"

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• The property names in JavaScript are usually just lowercase versions of the corresponding HTML attribute names

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Dynamic Styles

• Element’s style can be changed dynamically• Dynamic HTML Object Model also allows you to

change the class attribute

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<html > <head> <title>Object Model</title> <script type = "text/javascript">  </script> </head>

<body onload = "start()"> <p>Welcome to our Web site!</p> </body></html>

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<html> <head> <title>Object Model</title>

<style type = "text/css">

.bigText { font-size: 3em; font-weight: bold } .smallText { font-size: .75em }

</style> <script type = "text/javascript">  </script> </head>

<body onload = "start()">

<p id = "pText">Welcome to our Web site!</p> </body></html>

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Dynamic Positioning

• HTML elements can be positioned with scripting– Declare an element’s CSS position property to be either absolute or relative

– Move the element by manipulating any of the top, left, right or bottom CSS properties

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<html> <head> <title>Dynamic Positioning</title> <script type = "text/javascript">  </script>

</head> <body onload = "start()"> <p id = "pText" style = "position: absolute; left: 0; font-family: serif; color: blue"> Welcome!</p> </body></html>

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function run() { count += speed; if ( ( count % 200 ) == 0 ) { speed *= -1; direction = !direction; pText.style.color = ( speed < 0 ) ? "red" : "blue" ; firstLine = ( speed < 0 ) ? "Text shrinking" : "Text growing"; pText.style.fontFamily = fontStyle[ ++fontStylecount % 3 ]; } pText.style.fontSize = count / 3; pText.style.left = count; pText.innerHTML = firstLine + "<br /> Font size: " + count + "px"; }

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Using the frames Collection

• Referencing elements and objects in different frames by using the frames collection

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Index.html

<html>

<head>

<title>Frames collection</title>

</head>

<frameset rows = "100, *">

<frame src = "top.html" name = "upper" />

<frame src = "" name = "lower" />

</frameset>

</html>

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top.html<html xmlns = "http://www.w3.org/1999/xhtml"> <head> <title>The frames collection</title> <script type = "text/javascript">  </script> </head>

<body onload = "start()"> <h1>Cross-frame scripting!</h1> </body></html>

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navigator Object

• Netscape, Mozilla, Microsoft’s Internet Explorer– Others as well

• Contains information about the Web browser• Allows Web authors to determine what browser

the user is using

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<html> <head> <title>The navigator Object</title> <script type = "text/javascript">  </script> </head>

<body onload = "start()"> <p>Redirecting your browser to the appropriate page, please wait...</p> </body></html>

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Summary of the DHTML Object Model

applets

all

anchors

embeds

forms

filters

images

links

plugins

styleSheets

scripts

frames

plugins

collection

body

screen

document

history

navigator

location

event

document

document

object

window

Key

Fig. 13.10 DHTML Object Model.

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Object or collection Description Objects

window Represents the browser window and provides access to the document object contained in the window. If the window contains frames a separate window object is created automatically for each frame, to provide access to the document rendered in the frame. Frames are considered to be subwindows in the browser.

document Represents the XHTML document rendered in a window. The document object provides access to every element in the XHTML document and allows dynamic modification of the XHTML document.

body Provides access to the body element of an XHTML document. history Keeps track of the sites visited by the browser user. The object provides a script

programmer with the ability to move forward and backward through the visited sites, but for security reasons does not allow the actual site URLs to be manipulated.

navigator Contains information about the Web browser, such as the name of the browser, the version of the browser, the operating system on which the browser is running and other information that can help a script writer customize the user’s browsing experience.

location Contains the URL of the rendered document. When this object is set to a new URL, the browser immediately switches (navigates) to the new location.

event Can be used in an event handler to obtain information about the event that occurred (e.g., the mouse x-y coordinates during a mouse event).

screen Contains information about the computer screen for the computer on which the browser is running. Information such as the width and height of the screen in pixels can be used to determine the size at which elements should be rendered in a Web page.

Fig. 13.11 Objects in the Internet Explorer 6 Object Model.

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Summary of the DHTML Object ModelObject or collection Description Collections

all Many objects have an all collection that provides access to every element contained in the object. For example, the body object’s all collection provides access to every element in the body element of an XHTML document.

anchors Collection contains all the anchor elements (a) that have a name or id attribute. The elements appear in the collection in the order they were defined in the XHTML document.

applets Contains all the applet elements in the XHTML document. Currently, the most common applet elements are Java applets.

embeds Contains all the embed elements in the XHTML document.

forms Contains all the form elements in the XHTML document. The elements appear in the collection in the order they were defined in the XHTML document.

frames Contains window objects that represent each frame in the browser window. Each frame is treated as its own subwindow.

images Contains all the img elements in the XHTML document. The elements appear in the collection in the order they were defined in the XHTML document.

links Contains all the anchor elements (a) with an href property. This collection also contains all the area elements that represent links in an image map.


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Object or collection Description plugins Like the embeds collection, this collection contains all the embed elements in the

XHTML document. scripts Contains all the script elements in the XHTML document.

styleSheets Contains styleSheet objects that represent each style element in the XHTML document and each style sheet included in the XHTML document via link.


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Event Model

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Introduction

• Event model– Scripts can respond to user– Content becomes more dynamic– Interfaces become more intuitive

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Event onclick• onClick

– Invoked when user clicks the mouse on a specific item

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<html> <head> <title>DHTML Event Model - onclick</title>

<script type = "text/javascript" for = "para" event = "onclick">

 </script> </head> <body>

 <p id = "para">Click on this text!</p>  <input type = "button" value = "Click Me!" onclick = "alert( 'Hi again' )" /> </body></html>

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Event onload

• onload event– Fires when an element finishes loading– Used in the body element– Initiates a script after the page loads into the

client

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<html> <head> <title>DHTML Event Model - onload</title> <script type = "text/javascript">  </script> </head>

<body onload = "startTimer()"> <p>Seconds you have spent viewing this page so far: <strong id = "soFar">0</strong></p> </body></html>

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Error Handling with onerror

• onerror event– Execute specialized error-handling code

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<html> <head> <title>DHTML Event Model - onerror</title> <script type = "text/javascript">  </script> </head> <body>

<input id = "mybutton" type = "button" value = "Click Me!" onclick = "doThis()" /> </body></html>

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Tracking the Mouse with Event onmousemove

• onmousemove– Fires repeatedly when the user moves the

mouse over the Web page– Gives position of the mouse

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<html> <head> <title>DHTML Event Model - onmousemove event</title>

<script type = "text/javascript">  </script> </head>

<body style = "background-color: wheat" onmousemove = "updateMouseCoordinates()">

<span id = "coordinates">(0, 0)</span><br /> <img src = "deitel.gif" style = "position: absolute; top: 100; left: 100" alt = "Deitel" /> </body></html>

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Rollovers with onmouseover and onmouseout

• Two more events fired by mouse movements– onmouseover

• Mouse cursor moves over element

– Onmouseout• Mouse cursor leaves element

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<html> <head> <title> DHTML Event Model - onmouseover and onmouseout </title> <script type = "text/javascript"> <!--

captionImage1 = new Image(); captionImage1.src = "caption1.gif"; captionImage2 = new Image(); captionImage2.src = "caption2.gif"; function mOver() { if ( event.srcElement.id == "tableCaption" ) { event.srcElement.src = captionImage2.src; return; } if ( event.srcElement.id ) event.srcElement.style.color =

event.srcElement.id; }

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function mOut() { if ( event.srcElement.id == "tableCaption" ) { event.srcElement.src = captionImage1.src; return; } if ( event.srcElement.id ) event.srcElement.innerText = event.srcElement.id; } document.onmouseover = mOver; document.onmouseout = mOut; // --> </script> </head>

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<body style = "background-color: wheat"> <h1>Guess the Hex Code's Actual Color</h1> <p>Can you tell a color from its hexadecimal RGB code value? Look at the hex code, guess the color. To see what color it corresponds to, move the mouse over the hex code. Moving the mouse out will display the color name.</p> <table style = "width: 50%; border-style: groove; text-align: center; font-family: monospace; font-weight: bold">

<caption> <img src = "caption1.gif" id = "tableCaption" alt =

"Table Caption" /> </caption> <tr> <td id = "Black">#000000</td> <td id = "Blue">#0000FF</td> <td id = "Magenta">#FF00FF</td> <td id = "Gray">#808080</td> </tr> </table> </body></html>

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Rollovers with onmouseover and onmouseout

Property of event Description altkey This value is true if Alt key was pressed when event fired.

button Returns which mouse button was pressed by user (1: left-mouse button, 2: right-mouse button, 3: left and right buttons, 4: middle button, 5: left and middle buttons, 6: right and middle buttons, 7: all three buttons).

cancelBubble Set to false to prevent this event from bubbling (see Section 14.9, “Event Bubbling”).

clientX / clientY The coordinates of the mouse cursor inside the client area (i.e., the active area where the Web page is displayed, excluding scrollbars, navigation buttons, etc.).

ctrlKey This value is true if Ctrl key was pressed when event fired. offsetX / offsetY The coordinates of the mouse cursor relative to the object that fired the event.

propertyName The name of the property that changed in this event. recordset A reference to a data field’s recordset (see Chapter 16, “Data Binding”). returnValue Set to false to cancel the default browser action. screenX / screenY The coordinates of the mouse cursor on the screen coordinate system. shiftKey This value is true if Shift key was pressed when event fired. srcElement A reference to the object that fired the event. type The name of the event that fired. x / y The coordinates of the mouse cursor relative to this element’s parent

element. Fig. 14.5 Some event object properties.

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Form Processing with onfocus and onblur

• onfocus event fires when element gains focus

• onblur event fires when element loses focus

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<html> <head> <title>DHTML Event Model - onfocus and onblur</title> <script type = "text/javascript">  </script> </head> <body>

<form id = "myForm" action = ""> Name: <input type = "text" name = "name" onfocus = "helpText(0)" onblur = "helpText(6)" /><br />….</form> </body></html>

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More Form Processing with onsubmit and onreset

• onsubmit and onreset are useful events for processing forms

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<html> <head> <title> DHTML Event Model - onsubmit and onreset events </title> <script type = "text/javascript">  </script> </head>

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<body> <form id = "myForm" onsubmit = "formSubmit()" onreset = "formReset()" action = ""> Name: <input type = "text" name = "name" onfocus = "helpText(0)" onblur = "helpText(6)"

/><br /> <input type = "submit" value = "Submit" onfocus = "helpText(4)" onblur = "helpText(6)" /> <input type = "reset" value = "Reset" onfocus = "helpText(5)" onblur = "helpText(6)" /> </form> </body></html>

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Event Bubbling

• Crucial part of the event model

• Process whereby events fired in child elements “bubble” up to their parent elements

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<html xmlns = "http://www.w3.org/1999/xhtml"> <head> <title>DHTML Event Model - Event Bubbling</title> <script type = "text/javascript">  </script> </head> <body>

<p onclick = "paragraphClick( false )">Click here!</p> <p onclick = "paragraphClick( true )">Click here, too!</p> </body></html>

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More DHTML Events

• Remaining DHTML events and their descriptions

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More DHTML EventsEvent Description Clipboard events

onbeforecut Fires before a selection is cut to the clipboard. onbeforecopy Fires before a selection is copied to the clipboard. onbeforepaste Fires before a selection is pasted from the clipboard. oncopy Fires when a selection is copied to the clipboard. oncut Fires when a selection is cut to the clipboard. onabort Fires if image transfer has been interrupted by user. onpaste Fires when a selection is pasted from the clipboard. Data binding events onafterupdate Fires immediately after a databound object has been updated. onbeforeupdate Fires before a data source is updated. oncellchange Fires when a data source has changed. ondataavailable Fires when new data from a data source become available. ondatasetchanged Fires when content at a data source has changed. ondatasetcomplete Fires when transfer of data from the data source has

completed. onerrorupdate Fires if an error occurs while updating a data field. onrowenter Fires when a new row of data from the data source is

available. onrowexit Fires when a row of data from the data source has just

finished. onrowsdelete Fires when a row of data from the data source is deleted. onrowsinserted Fires when a row of data from the data source is inserted. Fig. 14.10 Dynamic HTML events.

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More DHTML EventsEvent Description Keyboard events

onhelp Fires when the user initiates help (i.e., by pressing the F1 key). onkeydown Fires when the user pushes down a key. onkeypress Fires when the user presses a key. onkeyup Fires when the user ends a key press. Marquee events onbounce Fires when a scrolling marquee bounces back in the other

direction. onfinish Fires when a marquee finishes its scrolling. onstart Fires when a marquee begins a new loop. Mouse events oncontextmenu Fires when the context menu is shown (right-click). ondblclick Fires when the mouse is double clicked. ondrag Fires during a mouse drag. ondragend Fires when a mouse drag ends. ondragenter Fires when something is dragged onto an area. ondragleave Fires when something is dragged out of an area. ondragover Fires when a drag is held over an area. ondragstart Fires when a mouse drag begins.

ondrop Fires when a mouse button is released over a valid target during a drag.

onmousedown Fires when a mouse button is pressed down. Fig. 14.10 Dynamic HTML events.

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More DHTML EventsEvent Description onmouseup Fires when a mouse button is released. Miscellaneous events onafterprint Fires immediately after the document prints. onbeforeeditfocus Fires before an element gains focus for editing. onbeforeprint Fires before a document is printed. onbeforeunload Fires before a document is unloaded (i.e., the window was closed or a link was

clicked). onchange Fires when a new choice is made in a select element, or when a text input is

changed and the element loses focus. onfilterchange Fires when a filter changes properties or finishes a transition (see Chapter 15,

Dynamic HTML: Filters and Transitions). onlosecapture Fires when the releaseCapture method is invoked. onpropertychange Fires when the property of an object is changed. onreadystatechange Fires when the readyState property of an element

changes. onreset Fires when a form resets (i.e., the user clicks a reset button). onresize Fires when the size of an object changes (i.e., the user resizes a window or frame). onscroll Fires when a window or frame is scrolled. onselect Fires when a text selection begins (applies to input or

textarea). onselectstart Fires when the object is selected. onstop Fires when the user stops loading the object. onunload Fires when a page is about to unload.

Fig. 14.10 Dynamic HTML events.

1 Introduction to Web Application Implement JavaScript in HTML.

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