jquery插件ScrollTo，jquery滚动到指定位置，为什么老外的JS就这么牛逼呢？与我自己写起来的插件相差不是一两米啊

/** * jQuery.ScrollTo * Copyright (c) 2007-2008 Ariel Flesler - aflesler(at)gmail(dot)com | http://flesler.blogspot.com * Dual licensed under MIT and GPL. * Date: 9/11/2008 * * @projectDescription Easy element scrolling using jQuery. * http://flesler.blogspot.com/2007/10/jqueryscrollto.html * Tested with jQuery 1.2.6. On FF 2/3, IE 6/7, Opera 9.2/5 and Safari 3. on Windows. * * @author Ariel Flesler * @version 1.4 * * @id jQuery.scrollTo * @id jQuery.fn.scrollTo * @param {String, Number, DOMElement, jQuery, Object} target Where to scroll the matched elements. *	  The different options for target are: *		- A number position (will be applied to all axes). *		- A string position ('44', '100px', '+=90', etc ) will be applied to all axes *		- A jQuery/DOM element ( logically, child of the element to scroll ) *		- A string selector, that will be relative to the element to scroll ( 'li:eq(2)', etc ) *		- A hash { top:x, left:y }, x and y can be any kind of number/string like above. * @param {Number} duration The OVERALL length of the animation, this argument can be the settings object instead. * @param {Object,Function} settings Optional set of settings or the onAfter callback. *	 @option {String} axis Which axis must be scrolled, use 'x', 'y', 'xy' or 'yx'. *	 @option {Number} duration The OVERALL length of the animation. *	 @option {String} easing The easing method for the animation. *	 @option {Boolean} margin If true, the margin of the target element will be deducted from the final position. *	 @option {Object, Number} offset Add/deduct from the end position. One number for both axes or { top:x, left:y }. *	 @option {Object, Number} over Add/deduct the height/width multiplied by 'over', can be { top:x, left:y } when using both axes. *	 @option {Boolean} queue If true, and both axis are given, the 2nd axis will only be animated after the first one ends. *	 @option {Function} onAfter Function to be called after the scrolling ends.  *	 @option {Function} onAfterFirst If queuing is activated, this function will be called after the first scrolling ends. * @return {jQuery} Returns the same jQuery object, for chaining. * * @desc Scroll to a fixed position * @example $('div').scrollTo( 340 ); * * @desc Scroll relatively to the actual position * @example $('div').scrollTo( '+=340px', { axis:'y' } ); * * @dec Scroll using a selector (relative to the scrolled element) * @example $('div').scrollTo( 'p.paragraph:eq(2)', 500, { easing:'swing', queue:true, axis:'xy' } ); * * @ Scroll to a DOM element (same for jQuery object) * @example var second_child = document.getElementById('container').firstChild.nextSibling; *			$('#container').scrollTo( second_child, { duration:500, axis:'x', onAfter:function(){ *				alert('scrolled!!');																    *			}}); * * @desc Scroll on both axes, to different values * @example $('div').scrollTo( { top: 300, left:'+=200' }, { axis:'xy', offset:-20 } ); */;(function( $ ){	var $scrollTo = $.scrollTo = function( target, duration, settings ){		$(window).scrollTo( target, duration, settings );	};	$scrollTo.defaults = {		axis:'y',		duration:1	};	// Returns the element that needs to be animated to scroll the window.	// Kept for backwards compatibility (specially for localScroll & serialScroll)	$scrollTo.window = function( scope ){		return $(window).scrollable();	};	// Hack, hack, hack... stay away!	// Returns the real elements to scroll (supports window/iframes, documents and regular nodes)	$.fn.scrollable = function(){		return this.map(function(){			// Just store it, we might need it			var win = this.parentWindow || this.defaultView,				// If it's a document, get its iframe or the window if it's THE document				elem = this.nodeName == '#document' ? win.frameElement || win : this,				// Get the corresponding document				doc = elem.contentDocument || (elem.contentWindow || elem).document,				isWin = elem.setInterval;			return elem.nodeName == 'IFRAME' || isWin && $.browser.safari ? doc.body				: isWin ? doc.documentElement				: this;		});	};	$.fn.scrollTo = function( target, duration, settings ){		if( typeof duration == 'object' ){			settings = duration;			duration = 0;		}		if( typeof settings == 'function' )			settings = { onAfter:settings };		settings = $.extend( {}, $scrollTo.defaults, settings );		// Speed is still recognized for backwards compatibility		duration = duration || settings.speed || settings.duration;		// Make sure the settings are given right		settings.queue = settings.queue && settings.axis.length > 1;		if( settings.queue )			// Let's keep the overall duration			duration /= 2;		settings.offset = both( settings.offset );		settings.over = both( settings.over );		return this.scrollable().each(function(){			var elem = this,				$elem = $(elem),				targ = target, toff, attr = {},				win = $elem.is('html,body');			switch( typeof targ ){				// A number will pass the regex				case 'number':				case 'string':					if( /^([+-]=)?/d+(px)?$/.test(targ) ){						targ = both( targ );						// We are done						break;					}					// Relative selector, no break!					targ = $(targ,this);				case 'object':					// DOMElement / jQuery					if( targ.is || targ.style )						// Get the real position of the target 						toff = (targ = $(targ)).offset();			}			$.each( settings.axis.split(''), function( i, axis ){				var Pos	= axis == 'x' ? 'Left' : 'Top',					pos = Pos.toLowerCase(),					key = 'scroll' + Pos,					old = elem[key],					Dim = axis == 'x' ? 'Width' : 'Height',					dim = Dim.toLowerCase();				if( toff ){// jQuery / DOMElement					attr[key] = toff[pos] + ( win ? 0 : old - $elem.offset()[pos] );					// If it's a dom element, reduce the margin					if( settings.margin ){						attr[key] -= parseInt(targ.css('margin'+Pos)) || 0;						attr[key] -= parseInt(targ.css('border'+Pos+'Width')) || 0;					}					attr[key] += settings.offset[pos] || 0;					if( settings.over[pos] )						// Scroll to a fraction of its width/height						attr[key] += targ[dim]() * settings.over[pos];				}else					attr[key] = targ[pos];				// Number or 'number'				if( /^/d+$/.test(attr[key]) )					// Check the limits					attr[key] = attr[key] <= 0 ? 0 : Math.min( attr[key], max(Dim) );				// Queueing axes				if( !i && settings.queue ){					// Don't waste time animating, if there's no need.					if( old != attr[key] )						// Intermediate animation						animate( settings.onAfterFirst );					// Don't animate this axis again in the next iteration.					delete attr[key];				}			});						animate( settings.onAfter );						function animate( callback ){				$elem.animate( attr, duration, settings.easing, callback && function(){					callback.call(this, target, settings);				});			};			function max( Dim ){				var attr ='scroll'+Dim,					doc = elem.ownerDocument;				return win						? Math.max( doc.documentElement[attr], doc.body[attr]  )						: elem[attr];			};		}).end();	};	function both( val ){		return typeof val == 'object' ? val : { top:val, left:val };	};})( jQuery );