//獲取元素的真實的，最終的CSS樣式屬性值的函數
function getStyle(elem,name){
if(elem.style[name]){
return elem.style[name];
}else if(elem.currentStyle){
return elem.currentStyle[name];
}else if(document.defaultView && document.defaultView.getComputedStyle){
name = name.replace(/([A-Z])/g,"-$1");
name = name.toLowerCase();

var s = document.defaultView.getComputedStyle(elem,"");
return s && s.getPropertyValue(name);
}else{
return null;
}
}
//兩個確定元素相對于整個文檔的X和Y位置的輔助位置
function pageX(elem){
return elem.offsetParent?
elem.offsetLeft+pageX(elem.offsetParent):
elem.offsetLeft;
}

function pageY(elem){
return elem.offsetParent?
elem.offsetTop+pageY(elem.offsetParent):
elem.offsetTop;
}
//確定元素相對于父親的位置的兩個函數
function parentX(elem){
return elem.parentNode == elem.offsetParent?
elem.offsetLeft:
pageX(elem)-pageX(elem.parentNode);
}

function parentY(elem){
return elem.parentNode==elem.offsetParent?
elem.offsetTop:
pageY(elem)-pageY(elem.parentNode);
}
//確定元素相對于它的CSS容器的位置
function posX(elem){
return parseInt(getStyle(elem,"left"));
}
function posY(elem){
return parseInt(getStyle(elem,"top"));
}
//設置元素x和y位置(與當前位置無關)的函數
function setX(elem,pos){
elem.style.left = pos+"px";
}
function setY(elem,pos){
elem.style.top = pos+"px";
}
//調整元素相對于當前位置的距離的函數
function addX(elem,pos){
setX(posX(elem)+pos);
}
function addY(elem,pos){
setY(posY(elem)+pos);
}

//獲取元素當前的高度和寬度
function getHeight(elem){
return parseInt(getStyle(elem,'height'));
}
function getWidth(elem){
return parseInt(getStyle(elem,'width'));
}
//即是元素隱藏，也能分別獲取它潛在的完整高度和寬度的兩個函數
function fullHeight(elem){
if(getStyle(elem,'display')!='none'){
return elem.offsetHeight||getHeight(elem);
}
var old = resetCSS(elem,{
display:'',
visibility:'hidden',
position:'absolute'
});
var h = elem.clientHeight||getHeight(elem);
restoreCSS(elem,old);
return h;
}

function fullWidth(elem){
if(getStyle(elem,'display')!='none'){
return elem.offsetWidth || getWidth(elem);
}
var old = resetCSS(elem,{
display:'',
visibility:'hidden',
position:'absolute'
});
var w = elem.clientWidth || getWidth(elem);
restoreCSS(elem,old);
return w;
}

function resetCSS(elem,prop){
var old = [];
for(var i in prop){
old[i] = elem.style[i];
elem.style[i] = prop[i];
}
return old;
}
function restoreCSS(elem,prop){
for(var i in prop){
elem.style[i] = prop[i];
}
}
//使用CSS的display屬性來切換元素可見性的一組函數
function hide(elem){
var curDisplay = getStyle(elem,'display');
if(curDisplay != 'none'){
elem.$oldDisplay= curDisplay;
}
elem.style.display = 'none';
}
function show(elem){
elem.style.display = elem.$oldDisplay ||'';

}
//設置元素的透明度
function setOpacity(elem,level){
if(elem.filters){
elem.style.filters = 'alpha(opacity='+level+')';
}else{
elem.style.opacity = level/100;
}
}

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