getComputedStyle for IE < 9

IElt9_getComputedStyle.js

void function() {
	var global = this


		/** @const */
		, _Array_slice = Array.prototype.slice

		/** @const */
		, _Function_apply = Function.prototype.apply

		/** @const */
		, _Function_call = Function.prototype.call

		/** Use native "bind" or unsafe bind for service and performance needs
		 * @const
		 * @param {Object} object
		 * @param {...} var_args
		 * @return {Function} */
		, _unSafeBind = Function.prototype.bind || function(object, var_args) {
			var __method = this,
				args = _Array_slice.call(arguments, 1);
			return function () {
				return _Function_apply.call(__method, object, args.concat(_Array_slice.call(arguments)));
			}
		}

		/** @const */
		, STRING_FOR_RE_style_important = "\\s*:\\s*(\\S+)\\s*(?:[$;]|(?:(!important)\\s*[$;]))"

		, _CSSStyleDeclaration_prototype_methods = {
			/**
			 * @param {String} propertyName
			 * @return String
			 */
			"getPropertyValue" : function(propertyName) {
				return this.getAttribute(propertyName);
			}
			/**
			 * @param {String} propertyName
			 * @return String
			 */
			, "removeProperty" : function(propertyName) {
				this.removeAttribute(propertyName);
			}
			/**
			 * @param {String} propertyName
			 * @param {String} value
			 * @param {String} priority
			 * @return void
			 */
			, "setProperty" : function(propertyName, value, priority) {
				if(priority != "important") {
					this.setAttribute(propertyName, value);
				}
				else {
					var reg = new RegExp(propertyName + STRING_FOR_RE_style_important, "i")
						, val = ";" + propertyName + ":" + value + " !important;"
						;
					if(reg.test(this.cssText)) {
						this.cssText = this.cssText.replace(reg, val)
					}
					else this.cssText = this.cssText + val;
				}
			}
			/**
			 @param {String} propertyName
			 @return String
			 */
			, "getPropertyPriority" : function(propertyName) {
				var reg = new RegExp(propertyName + STRING_FOR_RE_style_important, "i");
				return ((this.cssText || "").match(reg) || [])[2] || "";
			}
			/**
			 @param {Number} index
			 @return String
			 */
			, "item" : function(index) {
				//TODO::
			}
		}

		/** @const */
		, RE_style_alpha_filter = /alpha\(opacity=([^\)]+)\)/
		/** @type {Function}
	 	* @this {Node} */
		, style_getOpacityFromMSFilter = function() {
			var val = (this.filter || "").match(RE_style_alpha_filter);

			return val ? (parseInt(val[1]) / 100) + "" : "";//can't replace parseInt to '+(val[1])'
		}
		
		, _throwDOMException = function(msg) {
			throw new Error(msg);
		}
	;

	if( /\[native\scode\]/.test( global.getComputedStyle ) )return;


	/**
	 * @link https://developer.mozilla.org/en/DOM/window.getComputedStyle
	 * getCurrentStyle - функция возвращяет текущий стиль элемента
	 * @param {?Node} element HTML-Элемент
	 * @param {?string} pseudoElt A string specifying the pseudo-element to match. Must be null (or not specified) for regular elements.
	 * @this {Window}
	 * @return {CSSStyleDeclaration} Стиль элемента
	 */
	global.getComputedStyle = function(element, pseudoElt) {
		var _currentStyle = element.currentStyle || element.runtimeStyle;
		if(!("getPropertyValue" in _currentStyle)) {
			element.runtimeStyle.getPropertyValue = _CSSStyleDeclaration_prototype_methods["getPropertyValue"].bind(element);

			element.runtimeStyle.setProperty = element.runtimeStyle.removeProperty = function() {
				_throwDOMException("NO_MODIFICATION_ALLOWED_ERR");
			};

			element.runtimeStyle.getPropertyPriority = function(propertyName) {
				//TODO: tests
				return "";
			};
			element.runtimeStyle.item = _CSSStyleDeclaration_prototype_methods["item"];
		}

		var propDescription
			, _CSSStyleDeclProt
		;
		if((_CSSStyleDeclProt = global["CSSStyleDeclaration"]) && (_CSSStyleDeclProt = _CSSStyleDeclProt.prototype) && (!("float" in _currentStyle) || !("opacity" in _currentStyle))) {
			if(!("float" in _currentStyle)) {//TODO:: testing
				propDescription = Object.getOwnPropertyDescriptor(_CSSStyleDeclProt, "float");
				if(propDescription) {
					delete _CSSStyleDeclProt["float"];
				}
				Object.defineProperty(element.runtimeStyle, "float", {
					value : {
						valueOf : _unSafeBind.call(function(){
							return this.runtimeStyle.styleFloat || this.style.styleFloat
						}, element)
					}
				});
				if(propDescription) {
					Object.defineProperty(_CSSStyleDeclProt, "float", propDescription);
				}
			}

			if(!("opacity" in _currentStyle)) {//TODO:: testing
				propDescription = Object.getOwnPropertyDescriptor(_CSSStyleDeclProt, "opacity");
				if(propDescription) {
					delete _CSSStyleDeclProt["opacity"];
				}
				Object.defineProperty(element.runtimeStyle, "opacity", {
					value : {
						valueOf : _unSafeBind.call(function(){
							return this.runtimeStyle["msOpacity"] || this.style["msOpacity"] || style_getOpacityFromMSFilter.call(this.style) || style_getOpacityFromMSFilter.call(this.runtimeStyle);
						}, element)
					}
				});
				if(propDescription) {
					Object.defineProperty(_CSSStyleDeclProt, "opacity", propDescription);
				}
			}
		}
		else {
			if(!("float" in _currentStyle)) {
				element.runtimeStyle["float"] = {
					valueOf : _unSafeBind.call(function(){
						return this.runtimeStyle.styleFloat || this.style.styleFloat
					}, element)
				}
			}
			if(!("opacity" in _currentStyle)) {
				element.runtimeStyle["opacity"] = {
					valueOf : _unSafeBind.call(function(){
						return this.runtimeStyle["msOpacity"] || this.style["msOpacity"] || style_getOpacityFromMSFilter.call(this.style) || style_getOpacityFromMSFilter.call(this.runtimeStyle);
					}, element)
				}
			}
		}

		return element.currentStyle;
	}

}.call(this);