jquery/src/css.js

// exclude the following css properties to add px
var rexclude = /z-?index|font-?weight|opacity|zoom|line-?height/i,
	ralpha = /alpha\([^)]*\)/,
	ropacity = /opacity=([^)]*)/,
	rfloat = /float/i,
	rdashAlpha = /-([a-z])/ig,
	rupper = /([A-Z])/g,
	rnumpx = /^\d+(?:px)?$/i,
	rnum = /^\d/,

	// cache check for defaultView.getComputedStyle
	getComputedStyle = document.defaultView && document.defaultView.getComputedStyle,
	// normalize float css property
	styleFloat = jQuery.support.cssFloat ? "cssFloat" : "styleFloat",
	fcamelCase = function(all, letter){
		return letter.toUpperCase();
	};

jQuery.fn.css = function( name, value ) {
	var options = name, isFunction = jQuery.isFunction( value );

	if ( typeof name === "string" ) {
		// Are we setting the style?
		if ( value === undefined ) {
			return this.length ?
				jQuery.css( this[0], name ) :
				null;

		// Convert name, value params to options hash format
		} else {
			options = {};
			options[ name ] = value;
		}
	}
	
	var isFunction = {};
	
	// For each value, determine whether it's a Function so we don't
	// need to determine it again for each element
	for ( var prop in options ) {
		isFunction[prop] = jQuery.isFunction( options[prop] );
	}

	// For each element...
	for ( var i = 0, l = this.length; i < l; i++ ) {
		var elem = this[i];

		// Set all the styles
		for ( var prop in options ) {
			value = options[prop];

			if ( isFunction[prop] ) {
				value = value.call( elem, i );
			}

			if ( typeof value === "number" && !rexclude.test(prop) ) {
				value = value + "px";
			}

			jQuery.style( elem, prop, value );
		}
	}

	return this;
};

jQuery.extend({
	style: function( elem, name, value ) {
		// don't set styles on text and comment nodes
		if ( !elem || elem.nodeType === 3 || elem.nodeType === 8 ) {
			return undefined;
		}

		// ignore negative width and height values #1599
		if ( (name === "width" || name === "height") && parseFloat(value) < 0 ) {
			value = undefined;
		}

		var style = elem.style || elem, set = value !== undefined;

		// IE uses filters for opacity
		if ( !jQuery.support.opacity && name === "opacity" ) {
			if ( set ) {
				// IE has trouble with opacity if it does not have layout
				// Force it by setting the zoom level
				style.zoom = 1;

				// Set the alpha filter to set the opacity
				style.filter = (style.filter || "").replace( ralpha, "" ) +
					(parseInt( value ) + '' === "NaN" ? "" : "alpha(opacity=" + value * 100 + ")");
			}

			return style.filter && style.filter.indexOf("opacity=") >= 0 ?
				(parseFloat( ropacity.exec(style.filter)[1] ) / 100) + '':
				"";
		}

		// Make sure we're using the right name for getting the float value
		if ( rfloat.test( name ) ) {
			name = styleFloat;
		}

		name = name.replace(rdashAlpha, fcamelCase);

		if ( set ) {
			style[ name ] = value;
		}

		return style[ name ];
	},

	css: function( elem, name, force, extra ) {
		if ( name === "width" || name === "height" ) {
			var val, props = { position: "absolute", visibility: "hidden", display:"block" }, which = name === "width" ? [ "Left", "Right" ] : [ "Top", "Bottom" ];

			function getWH() {
				val = name === "width" ? elem.offsetWidth : elem.offsetHeight;

				if ( extra === "border" ) { return; }

				jQuery.each( which, function() {
					if ( !extra ) {
						val -= parseFloat(jQuery.curCSS( elem, "padding" + this, true)) || 0;
					}

					if ( extra === "margin" ) {
						val += parseFloat(jQuery.curCSS( elem, "margin" + this, true)) || 0;
					} else {
						val -= parseFloat(jQuery.curCSS( elem, "border" + this + "Width", true)) || 0;
					}
				});
			}

			if ( elem.offsetWidth !== 0 ) {
				getWH();
			} else {
				jQuery.swap( elem, props, getWH );
			}

			return Math.max(0, Math.round(val));
		}

		return jQuery.curCSS( elem, name, force );
	},

	curCSS: function( elem, name, force ) {
		var ret, style = elem.style, filter;

		// IE uses filters for opacity
		if ( !jQuery.support.opacity && name === "opacity" && elem.currentStyle ) {
			ret = ropacity.test(elem.currentStyle.filter || "") ?
				(parseFloat(RegExp.$1) / 100) + "" :
				"";

			return ret === "" ?
				"1" :
				ret;
		}

		// Make sure we're using the right name for getting the float value
		if ( rfloat.test( name ) ) {
			name = styleFloat;
		}

		if ( !force && style && style[ name ] ) {
			ret = style[ name ];

		} else if ( getComputedStyle ) {

			// Only "float" is needed here
			if ( rfloat.test( name ) ) {
				name = "float";
			}

			name = name.replace( rupper, "-$1" ).toLowerCase();

			var computedStyle = elem.ownerDocument.defaultView.getComputedStyle( elem, null );

			if ( computedStyle ) {
				ret = computedStyle.getPropertyValue( name );
			}

			// We should always get a number back from opacity
			if ( name === "opacity" && ret === "" ) {
				ret = "1";
			}

		} else if ( elem.currentStyle ) {
			var camelCase = name.replace(rdashAlpha, fcamelCase);

			ret = elem.currentStyle[ name ] || elem.currentStyle[ camelCase ];

			// From the awesome hack by Dean Edwards
			// http://erik.eae.net/archives/2007/07/27/18.54.15/#comment-102291

			// If we're not dealing with a regular pixel number
			// but a number that has a weird ending, we need to convert it to pixels
			if ( !rnumpx.test( ret ) && rnum.test( ret ) ) {
				// Remember the original values
				var left = style.left, rsLeft = elem.runtimeStyle.left;

				// Put in the new values to get a computed value out
				elem.runtimeStyle.left = elem.currentStyle.left;
				style.left = ret || 0;
				ret = style.pixelLeft + "px";

				// Revert the changed values
				style.left = left;
				elem.runtimeStyle.left = rsLeft;
			}
		}

		return ret;
	},

	// A method for quickly swapping in/out CSS properties to get correct calculations
	swap: function( elem, options, callback ) {
		var old = {};

		// Remember the old values, and insert the new ones
		for ( var name in options ) {
			old[ name ] = elem.style[ name ];
			elem.style[ name ] = options[ name ];
		}

		callback.call( elem );

		// Revert the old values
		for ( var name in options ) {
			elem.style[ name ] = old[ name ];
		}
	}
});