JavaScript IV Robin Burke ECT 270

Outline Final project reminder Style review Manipulating style Special effect examples

Final project Grading rubric fill in for your team bring to class next week

Quick review of style Introduced in the context of CSS but can be embedded in particular tags Style is a specification language for layout Specify colors font properties position

Style Syntax element-name {style-name1: property1; style-name2: property2} h1 { font-weight: bold; font-family: sans-serif; } Or embedded style Title here

Example style sheet for course site

Manipulating style We can manipulate style dynamically just like other element properties Each element has an associated style object setting the properties of this object change the element's displayed style editing embedded style

Note CSS "-" is style name separator font-family: Arial, sans-serif JavaScript "-" is subtraction operator style names use lowerUpper syntax font-family becomes fontFamily elem.style.fontFamily = "Arial, sans-serif" Netscape style property is missing from "schismatic" Netscape versions (4-5) instead elem.fontFamily =...

Cross-browser solution StyleAPI file if (document.layers) isNS = true; if (document.all) isIE = true; function setFontFamily (elem, family) { if (isIE) elem.style.fontFamily = family; else if (isNS) elem.fontFamily = family; }

Examples change font color change font family button example from 10/27

Manipulating position and boundary Position is another style property also boundary via clip property Many effects possible animation drop down menus

Implementation Relevant DOM properties elem.style.left elem.style.top Problem these are string values with units "5 px", "10 in" Solution IE-specific elem.style.pixelLeft integer valued use text processing parseInt to get value value + "px" to set

Animation Repeated display with transformation How to achieve repeat? looping is bad prevent the user from interacting with browser better solution use event mechanism setTimeout(fn, delay) the function will be called when the delay has passed

Animation examples linear shift path animation snowflakes

Controlling display Visibility elem.style.visibility = "hidden"; or "visible", "inherit" element takes up space but can't be seen elem.style.display = "none"; or "" element takes up no space

Controlling display, cont'd Clipping Can set the size of the container smaller than its contents elem.style.clip = rect(x1, y1, x2, y2);

Controlling display, cont'd Clipping creates a viewing area can't access the rest of the image or contents To shrink viewing area, but allow access change size of the element set overflow property

What to do with excess Use overflow property

Example scrollable HTML area

Drop-down effects Clipping can be used for drop-down menus purely in HTML no images

Before clipping After clipping

Note Book's DOM API is not needed with Mozilla Book's code is really ugly mine is better

CSS and JavaScript Discussed how to modify style of a single element one property at a time CSS lets us have classes We can modify an elements class at run-time elem.className=

Example rollover expandable outline

Modifying a style associated with a class Stylesheets themselves are objects Accessed via styleSheets[] array Each style sheet has an array of rules cssRules[] (NS) rules [] (IE) We can inspect and modify the styles

Example rollover

Next week Grading sheet Be here at 5:45 pm for presentations stay to hear your classmates