JAVASCRIPT初学者关于滑动门代码的疑问,求大神呀~

var currentSection = "home-pane"; // The default loaded section on the page
var tabTag = "-tab";
var paneTag = "-pane";
// Scroll the page manually to the position of element "link", passed to us.
function ScrollSection(link, scrollArea, offset)
{
// Store the last section, and update the current section
if (currentSection == link) {
return;
}
lastSection = currentSection;
currentSection = link;
// Change the section highlight.
// Extract the root section name, and use that to change the background image to *top*, revealing the alt. state
sectionTab = currentSection.split("-")[0] + tabTag;
document.getElementById(sectionTab).className = *active*;
if (lastSection) {
lastTab = lastSection.split("-")[0] + tabTag;
document.getElementById(lastTab).className = "inactive";
}
// Get the element we want to scroll, get the position of the element to scroll to
theScroll = document.getElementById(scrollArea);
position = findElementPos(document.getElementById(link));
// Get the position of the offset div -- the div at the far left.
// This is the amount we compensate for when scrolling
if (offset != "") {
offsetPos = findElementPos(document.getElementById(offset));
position[0] = position[0] - offsetPos[0];
}
scrollStart(theScroll, theScroll.scrollLeft, position[0], "horiz");
// return false;
}
function ScrollArrow(direction, toolbar, scrollArea, offset) {
toolbarElem = document.getElementById(toolbar);
toolbarNames = new Array();
// Find all the <li> elements in the toolbar, and extract their id*s into an array.
if (toolbarElem.hasChildNodes())
{
var children = toolbarElem.childNodes;
for (var i = 0; i < children.length; i++)
{
if (toolbarElem.childNodes[i].tagName == "LI") {
toolbarNames.push(toolbarElem.childNodes[i].id.split("-")[0]);
}
}
}
// Now iterate through our array of tab names, find matches, and determine where to go.
for (var i = 0; i < toolbarNames.length; i++) {
if (toolbarNames[i] == currentSection.split("-")[0]) {
if (direction == "left") {
if (i - 1 < 0) {
gotoTab = toolbarNames[toolbarNames.length - 1];
} else {
gotoTab = toolbarNames[i - 1];
}
} else {
if ((i + 1) > (toolbarNames.length - 1)) {
gotoTab = toolbarNames[0];
} else {
gotoTab = toolbarNames[i + 1];
}
}
}
}
// Go to the section name!
ScrollSection(gotoTab+paneTag, scrollArea, offset);
}
var scrollanim = {time:0, begin:0, change:0.0, duration:0.0, element:null, timer:null};
function scrollStart(elem, start, end, direction)
{
//console.log("scrollStart from "+start+" to "+end+" in direction "+direction);
if (scrollanim.timer != null) {
clearInterval(scrollanim.timer);
scrollanim.timer = null;
}
scrollanim.time = 0;
scrollanim.begin = start;
scrollanim.change = end - start;
scrollanim.duration = 25;
scrollanim.element = elem;
if (direction == "horiz") {
scrollanim.timer = setInterval("scrollHorizAnim();", 15);
}
else {
scrollanim.timer = setInterval("scrollVertAnim();", 15);
}
}
function scrollVertAnim()
{
if (scrollanim.time > scrollanim.duration) {
clearInterval(scrollanim.timer);
scrollanim.timer = null;
}
else {
move = sineInOut(scrollanim.time, scrollanim.begin, scrollanim.change, scrollanim.duration);
scrollanim.element.scrollTop = move;
scrollanim.time++;
}
}
function scrollHorizAnim()
{
if (scrollanim.time > scrollanim.duration) {
clearInterval(scrollanim.timer);
scrollanim.timer = null;
}
else {
move = sineInOut(scrollanim.time, scrollanim.begin, scrollanim.change, scrollanim.duration);
scrollanim.element.scrollLeft = move;
scrollanim.time++;
}
}
function findElementPos(elemFind) {
var elemX = 0;
var elemY = 0;
do {
elemX += elemFind.offsetLeft;
elemY += elemFind.offsetTop;
} while (elemFind = elemFind.offsetParent)
//console.log("Found element "+elemFind+" at "+elemY+"/"+elemX);
return Array(elemX, elemY);
}
function sineInOut(t, b, c, d) {
return -c / 2 * (Math.cos(Math.PI * t / d) - 1) + b;
}
求大神帮忙解释一下各个函数的意思,还有函数sineinOut的作用还有offsetParent和elemFind的概念,谢谢啦!!!!!!