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Standard based web design

Standard based web design. Overview of Dynamic HTML. What is DHTML?. D ynamic H ypertext M arkup L anguage is comprised of: CSS (cascading style sheets) DOM (document object module) Scripting ( Javascript and VBscript) Allows for more interactivity and special effects on web pages.

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Standard based web design

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  1. Standard based web design Overview of Dynamic HTML

  2. What is DHTML? Dynamic Hypertext Markup Language is comprised of: • CSS (cascading style sheets) • DOM (document object module) • Scripting (Javascript and VBscript) • Allows for more interactivity and special effects on web pages.

  3. Document Object Model (DOM) • DOM is an interface that permits scripts to access and update the content, structure and style of the document. • Every element of the web page can be dynamically updated in response to input from the user or other programs • HTML elements are treated as objects, their attributes are treated as properties of the objects • The DOM has a hierarchy of elements with the window as the top level object

  4. Object hierarchy: an example window.document.formName document.formName

  5. JavaScript • JavaScript is an object-based language: it is based on manipulating objects by modifying their properties or applying methods to them. • Objects are items that exist in a defined space in a Web page (window, document, form etc) • Each object has properties that describe its appearance, purpose, or behavior • An object can have methods, which are actions that can be performed with or to it.

  6. JavaScript and events • Certain objects and tags in HTML have corresponding events associated to them. • A button in a form can be clicked • JavaScript allows you to trigger action based on an event taking place, by using event handlers • onClick do this and that

  7. <!- - Hide this script from browsers that don’t support JavaScript // Stop hiding from other browsers - -> JavaScript and HTML • Place JavaScript commands in a separate file & link the HTML file to that file by using the <SCRIPT> tag in the head of the file <SCRIPT SRC=URL LANGUAGE=“javascript”> other script commands and comments</SCRIPT> • Place JavaScript commands directly in the HTML file (<SCRIPT> tag in the <HEAD> or the <BODY>) <SCRIPT LANGUAGE=“JavaScript”> script commands and comments</SCRIPT>

  8. A trivial example • document.lastModified reflects when the page was last modifieddocument is the objectlastModified is a property of document <script languange=“javaScript”>var modifiedDate=document.lastModified;document.write(modifiedDate);</script>

  9. The window object and methods • The window object represents a browser window. Window methods are • window.alert("string“); Shows an alert window with text string, and 'OK' button • window.prompt(“string of character”, “default value”);Prompts user for input • Window.confirm(“string”);If the OK button is clicked, the confirm method returns the value “true” • window.close(); • window.open(URL, windowname);

  10. Objects and their methods

  11. JavaScript events • An event is a specific action that triggers the browser to run a block of JavaScript commands

  12. Event handlers

  13. Working with object properties • Change the value of a property object.property = expressiondocument.bgColor=“red” • Save object property as a variablevariable = object.propertypageColor =document.bgColor

  14. JavaScript event handlers • An event handler is code added to an HTML tag. It is triggered when the associated event occurs within the tag <TAG event_handler =“JavaScript commands;”> <FORM><INPUT TYPE=RADIO onClick=“document.bgColor=‘red’;”>red<BR><INPUT TYPE=RADIO onClick=“document.bgColor=‘blue’;”>blue<BR></FORM> INPUT is the tag, onClick is the event, “document…” is the event handler

  15. Coming up • Form validation • Mathematical manipulations • Changing style: visibility,display,clip (menus) • Repeating commands (Slide shows, banners) • Filters and transitions • Moving object on the screen

  16. Validating forms You can use JavaScript to • Make sure that your form contain valid information • Check data in one field against data in another field (choose a new password) • Highlight incorrect information to let the user know what needs to be changed

  17. Form Validation • If passwd1 ==“”tell the user to enter a password and reposition the cursor to the correct field • If passwd1!=passwd2tell the user the 2 passwords don’t match and reposition the cursor <FORM NAME=“changePsw” > Your name: <INPUT TYPE="TEXT" SIZE="30"> <P>Choose a password: <INPUT TYPE="PASSWORD" NAME="passwd1"> <P>Verify password: <INPUT TYPE="PASSWORD" NAME="passwd2"> <P><INPUT TYPE="SUBMIT" VALUE="Submit"> <INPUT TYPE="RESET"> </FORM> onSubmit=“return checkform(this)”

  18. function validForm(passForm) { if (passForm.passwd1.value == "") { alert("You must enter a password"); passForm.passwd1.focus(); return false} else { if (passForm.passwd1.value != passForm.passwd2.value) { alert("Entered passwords did not match"); passForm.passwd1.focus();//return the cursor to the first password field passForm.passwd1.select();//select the entry in the first password field return false} else {return true} } } <FORM NAME="changePsw" onSubmit="return validForm(changePsw)" > or <FORM onSubmit="return validForm(this)" >

  19. More on forms • Copying the values entered in one field to another field • Convert F degrees into Celsius • A mortgage calculator

  20. Microsoft Object Hierarchy Key embeds links filters images forms styleSheets scripts plugins plugins history anchors all frames applets navigator screen collection document document document object location window body event Only in IE

  21. Netscape DOM

  22. Element collections • In JS you translate this hierarchy into reference names which indicate the location of the element in the DOM • Elements can be grouped into element collections which are arrays of all the elements of a particular type document.images.myImageID.property document.images[“myImageID”].property

  23. Referencing <DIV> tags Netscape (<div>s belong to the layers collection) document.layers.divID or document.divID I.E. (<div>s belong to the all collection) document.all.divID or divID Browser detection: var isNS=false; // True if user has Netscape var isIE=false; // True if user has Internet Explorer if (document.layers){isNS=true;} if (document.all){isIE=true;}

  24. Referencing Styles The syntax rules for changing one of the style attributes of an element in Netscape: objectID.attribute I.E. objectID.style.attribute • objectID is the name of the particular element (image, div, form field ..), style is a JS word, attribute is the specific attribute you are referring to (visibility, display …) • The attribute can’t contain “-”!background-color becomes backgroundColor

  25. W3C DOM (a farewell to DOM) • The W3C DOM doesn’t use the dot syntax to describe objects • The programmers uses the ID attribute (instead of NAME) to name each element in advance<IMG ID=myImage> • Use the getElementByID(tagID) tool to access that elementdocument.getElementByID(“myImage”) • Netscape 6, IE 5+, Opera 5+ etc

  26. Controlling object visibility Internet Explorer document.getElementById(“id”).visibility=“visible/hidden”; document.getElementById(“id”).display=“none”; document.getElementById(“id”).display=“block”; document.getElementById(“id”).clip=“rect(t,r,b,l)”;

  27. Before clipping After clipping

  28. Menus • Side menu: MSNBC MetraRail • Drop Down: T-Mobile In-Style Magazine

  29. Rollovers • DePaul website • Bloomingdale’s wedding channel • CBS

  30. Repeating commands clearInterval (variable); variable=setInterval(“fctName()”,# of millisec); tells the script to run the function fctName at the specified interval of milliseconds. Cancels the setInterval command

  31. Time delayed commands variable= setTimeout(“fctName()”,# of millisec); tells the script to run the function fctName after the specified number of milliseconds clearTimeout (variable); Cancels the time delayed command

  32. Cycling banner ads (images) adImages is an array containing the URLs of the banner images adBanner is the name in the <IMG> tag where the ads are displayed function next(){…document.adBanner.src=adImages[counter];setTimeout(“rotate()”,3*1000);…} Every 3 seconds the src of the image tag is updated

  33. Photo gallery and slide shows • Prev-Next: Chicago tribune • Automatic show: MSNBC

  34. Other effects • Scrolling news: metrarail • Filters • Increasing font size • Cursor Images

  35. Transition (special filters) • A transition is a visual effect applied to an object over an interval of time • blendTrans fades an object in and out. You have to specify a value for the Duration of the transitionobjectName.filters.blendTrans.Duration =2; orobjectName.style.filter=“blendTrans(Duration=2)”; • revealTrans in addition to the Duration it allows you to specify the type of the transition

  36. objectName.filters.revealTrans.Duration=2; // 2 seconds objectName.filters.revealTrans.Transition=5; //Wipe down orobjectName.style.filter=“revealTrans(Duration=2, Transition=5)”;

  37. Applying a transition • Set the initial state of the object(visibility, or source for an image file) • Apply a transition effect to the object(by using the apply() method)objectName.filters.transition_type.apply(); • Specify the final state of the object • Play the transition (use the play() method) objectName.filters.transition_type.play();

  38. Moving objects on the screen • Once an object is positioned in the HTML code using the position attribute in CSS, you can change the coordinates of the object using JavaScript attributes objectID.style.left or objectID.style.top how far the left/top edge of the object is from the parent element (100px). The value of these attributes may be changed dynamically

  39. function moveObjectTo(objectID,x,y){ moverObject=document.getElementById(objectID).style; moverObject.left =x; moverObject.top =y; } <IMG id=“mover” onClick=“moveObjectTo(mover,100,100)>

  40. Moving objects on the screen function slide(){ moverObject =document.getElementById(“mover”).style; moverObject.pixelLeft =moverObject.pixelLeft +2; if (moverObject.pixelLeft <= rightDotPos){ setTimeout(“slide()”, 20);} <BODY onLoad=“slide()”> <IMG ID=“mover” src=fullmoon.jpg>

  41. Window height and width IE: document.body.clientHeight document.body.clientWidth Are the body properties that indicates the dimension of the browser window. They are available only after the page is loaded. Netscape:window.innerHeight window.innerWidth Properties of the screen object will capture the dimension of the user’s monitor

  42. Linear animation (diagonally across) function moveText(){maxHeight = document.body.clientHeight –100; moverObject =document.getElementById(“mover”).style;moverObject.pixelLeft =moverObject.pixelLeft +2; moverObject.pixelTop =moverObject.pixelTop +2; if (moverObject.pixelLeft <= maxHeight){ setTimeout(“moveText()”, 20);} } <STYLE>#mover {position:absolute;left:5px;top:5px;}</STYLE> <DIV ID=mover”> On the Road again </DIV>

  43. Path animation • You are not restricted to linear paths for animation. You can have the object move from point to point along a path that has any shape you want • The x coordinate of each point in the path is stored into an array (x) • The y coordinate of each point is stored into another array (y)

  44. Path animation (spiral in) //store the consecutive increments in x and y (dx, and dy)x= new Array(0,20,40,80, … -100,-50, …);y= new Array(0,10,20,40, … -150, -80, …);index=0; function moveIt(objectID,dx,dy){moverObject =document.getElementById(objectID).style;moverObject.pixelLeft =moverObject.pixelLeft +dx; moverObject.pixelTop =moverObject.pixelTop +dy;} Function spiral(){ if (index <x.length-1){ moveIt(“mover”,x[index],y[index]); index++; setTimeout(“spiral()”, 100);} }

  45. End of Lecture

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