用javaScript确定元素位置的一些函数

/*
根据id判断位置，返回X,Y轴的坐标
*/
function getElementPos(elementId){
    var ua = navigator.userAgent.toLowerCase();
    var isOpera = (ua.indexOf('opera') != -1);
    var isIE = (ua.indexOf('msie') != -1 && !isOpera); // not opera spoof
    var el = document.getElementById(elementId);
    if (el.parentNode === null || el.style.display == 'none') {
        return false;
    }
    var parent = null;
    var pos = [];
    var box;
    if (el.getBoundingClientRect) // IE
    {
        box = el.getBoundingClientRect();
        var scrollTop = Math.max(document.documentElement.scrollTop, document.body.scrollTop);
        var scrollLeft = Math.max(document.documentElement.scrollLeft, document.body.scrollLeft);
        return {
            x: box.left + scrollLeft,
            y: box.top + scrollTop
        };
    }
    else 
        if (document.getBoxObjectFor) // gecko
        {
            box = document.getBoxObjectFor(el);
            var borderLeft = (el.style.borderLeftWidth) ? parseInt(el.style.borderLeftWidth) : 0;
            var borderTop = (el.style.borderTopWidth) ? parseInt(el.style.borderTopWidth) : 0;
            pos = [box.x - borderLeft, box.y - borderTop];
        }
        else // safari & opera
        {
            pos = [el.offsetLeft, el.offsetTop];
            parent = el.offsetParent;
            if (parent != el) {
                while (parent) {
                    pos[0] += parent.offsetLeft;
                    pos[1] += parent.offsetTop;
                    parent = parent.offsetParent;
                }
            }
            if (ua.indexOf('opera') != -1 ||
            (ua.indexOf('safari') != -1 && el.style.position == 'absolute')) {
                pos[0] -= document.body.offsetLeft;
                pos[1] -= document.body.offsetTop;
            }
        }
    if (el.parentNode) {
        parent = el.parentNode;
    }
    else {
        parent = null;
    }
    while (parent && parent.tagName != 'BODY' && parent.tagName != 'HTML') { // account for any scrolled ancestors
        pos[0] -= parent.scrollLeft;
        pos[1] -= parent.scrollTop;
        if (parent.parentNode) {
            parent = parent.parentNode;
        }
        else {
            parent = null;
        }
    }
    return {
        x: pos[0],
        y: pos[1]
    };
}

/*
 函数功能：
 兼容IE和FF返回目标对象包含边框的left、top、width、height值。其中left、top是相对于document.body的坐标。
 需要参数1个：
 [DOM]o=[DOM]要取值的对象。
 */
function getLTWH(id){
    o = jQuery("#"+id);
    if (o == null) {
        return;
    }
    function getCurrentStyle(style){
        var number = parseInt(o.currentStyle[style]);
        return isNaN(number) ? 0 : number;
    }
    function getComputedStyle(style){
        return parseInt(document.defaultView.getComputedStyle(o, null).getPropertyValue(style));
    }
    var oLTWH = {
        "left": o.offsetLeft,
        "top": o.offsetTop,
        "width": o.offsetWidth,
        "height": o.offsetHeight
    };
    while (true) {
        o = o.offsetParent;
        if (o == (document.body && null)) 
            break;
        oLTWH.left += o.offsetLeft;
        oLTWH.top += o.offsetTop;
        if (jQuery.browser.msie && jQuery.browser.version == "6.0") {
            oLTWH.left += getCurrentStyle("borderLeftWidth");
            oLTWH.top += getCurrentStyle("borderTopWidth");
        }
        else {
            oLTWH.left += getComputedStyle("border-left-width");
            oLTWH.top += getComputedStyle("border-top-width");
        }
    }
    return oLTWH;
}

function getltByWindow(){
    var windowWidth, windowHeight;// 窗口的高和宽
    // 取得窗口的高和宽
    if (self.innerHeight) {
        windowWidth = self.innerWidth;
        windowHeight = self.innerHeight;
    }
    else 
        if (document.documentElement &&
        document.documentElement.clientHeight) {
            windowWidth = document.documentElement.clientWidth;
            windowHeight = document.documentElement.clientHeight;
        }
        else 
            if (document.body) {
                windowWidth = document.body.clientWidth;
                windowHeight = document.body.clientHeight;
            }
    var loc = {
        left: windowWidth,
        top: windowHeight
    };
    return loc;
}