从YUI-Ext的插件中发现了这个插件用起来很是方便下面是使用的例子
比如获得id为testdiv的元素的位置，并将结果返回给变量test
var test=$("#testdiv").offset();
此时test的值为：{ top: 100, left: 100, scrollTop: 10, scrollLeft: 10 }
然后用起来非常方便：
比如他的位置就是test.top或者test.left,这样使用起来是不是很方便，呵呵！
/**
* Returns the location of the element in pixels from the top left corner of the viewport.
*
* For accurate readings make sure to use pixel values for margins, borders and padding.
*
* @example $("#testdiv").offset()
* @result { top: 100, left: 100, scrollTop: 10, scrollLeft: 10 }
*
* @example $("#testdiv").offset({ scroll: false })
* @result { top: 90, left: 90 }
*
* @example var offset = {}
* $("#testdiv").offset({ scroll: false }, offset)
* @result offset = { top: 90, left: 90 }
*
* @name offset
* @param Object options A hash of options describing what should be included in the final calculations of the offset.
* The options include:
* margin: Should the margin of the element be included in the calculations? True by default.
* If set to false the margin of the element is subtracted from the total offset.
* border: Should the border of the element be included in the calculations? True by default.
* If set to false the border of the element is subtracted from the total offset.
* padding: Should the padding of the element be included in the calculations? False by default.
* If set to true the padding of the element is added to the total offset.
* scroll: Should the scroll offsets of the parent elements be included in the calculations?
* True by default. When true, it adds the total scroll offsets of all parents to the
* total offset and also adds two properties to the returned object, scrollTop and
* scrollLeft. If set to false the scroll offsets of parent elements are ignored.
* If scroll offsets are not needed, set to false to get a performance boost.
* @param Object returnObject An object to store the return value in, so as not to break the chain. If passed in the
* chain will not be broken and the result will be assigned to this object.
* @type Object
* @cat Plugins/Dimensions
* @author Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net)
*/
jQuery.fn.offset = function(options, returnObject) {
var x = 0, y = 0, elem = this[0], parent = this[0], sl = 0, st = 0, options = jQuery.extend({ margin: true, border: true, padding: false, scroll: true }, options || {});
do {
x += parent.offsetLeft || 0;
y += parent.offsetTop || 0;
// Mozilla and IE do not add the border
if (jQuery.browser.mozilla || jQuery.browser.msie) {
// get borders
var bt = parseInt(jQuery.css(parent, 'borderTopWidth')) || 0;
var bl = parseInt(jQuery.css(parent, 'borderLeftWidth')) || 0;
// add borders to offset
x += bl;
y += bt;
// Mozilla removes the border if the parent has overflow property other than visible
if (jQuery.browser.mozilla && parent != elem && jQuery.css(parent, 'overflow') != 'visible') {
x += bl;
y += bt;
}
}
var op = parent.offsetParent;
if (op && (op.tagName == 'BODY' || op.tagName == 'HTML')) {
// Safari doesn't add the body margin for elments positioned with static or relative
if (jQuery.browser.safari && jQuery.css(parent, 'position') != 'absolute') {
x += parseInt(jQuery.css(op, 'marginLeft')) || 0;
y += parseInt(jQuery.css(op, 'marginTop')) || 0;
}
// Exit the loop
break;
}
if (options.scroll) {
// Need to get scroll offsets in-between offsetParents
do {
sl += parent.scrollLeft || 0;
st += parent.scrollTop || 0;
parent = parent.parentNode;
// Mozilla removes the border if the parent has overflow property other than visible
if (jQuery.browser.mozilla && parent != elem && parent != op && parent.style && jQuery.css(parent, 'overflow') != 'visible') {
y += parseInt(jQuery.css(parent, 'borderTopWidth')) || 0;
x += parseInt(jQuery.css(parent, 'borderLeftWidth')) || 0;
}
} while (parent != op);
} else {
parent = parent.offsetParent;
}
} while (parent);
if ( !options.margin) {
x -= parseInt(jQuery.css(elem, 'marginLeft')) || 0;
y -= parseInt(jQuery.css(elem, 'marginTop')) || 0;
}
// Safari and Opera do not add the border for the element
if ( options.border && (jQuery.browser.safari || jQuery.browser.opera) ) {
x += parseInt(jQuery.css(elem, 'borderLeftWidth')) || 0;
y += parseInt(jQuery.css(elem, 'borderTopWidth')) || 0;
} else if ( !options.border && !(jQuery.browser.safari || jQuery.browser.opera) ) {
x -= parseInt(jQuery.css(elem, 'borderLeftWidth')) || 0;
y -= parseInt(jQuery.css(elem, 'borderTopWidth')) || 0;
}
if ( options.padding ) {
x += parseInt(jQuery.css(elem, 'paddingLeft')) || 0;
y += parseInt(jQuery.css(elem, 'paddingTop')) || 0;
}
// Opera thinks offset is scroll offset for display: inline elements
if (options.scroll && jQuery.browser.opera && jQuery.css(elem, 'display') == 'inline') {
sl -= elem.scrollLeft || 0;
st -= elem.scrollTop || 0;
}
var returnValue = options.scroll ? { top: y - st, left: x - sl, scrollTop: st, scrollLeft: sl }
: { top: y, left: x };
if (returnObject) { jQuery.extend(returnObject, returnValue); return this; }
else { return returnValue; }
};