Index: src/core.js
===================================================================
--- src/core.js	(revision 5946)
+++ src/core.js	(working copy)
@@ -41,7 +41,7 @@
 			return this;
 		}
 		// Handle HTML strings
-		if ( typeof selector == "string" ) {
+		if ( typeof selector === "string" ) {
 			// Are we dealing with HTML string or an ID?
 			var match = quickExpr.exec( selector );
 
@@ -150,7 +150,7 @@
 		var options = name;
 
 		// Look for the case where we're accessing a style value
-		if ( name.constructor == String )
+		if ( typeof name === "string" )
 			if ( value === undefined )
 				return this[0] && jQuery[ type || "attr" ]( this[0], name );
 
@@ -180,7 +180,7 @@
 	},
 
 	text: function( text ) {
-		if ( typeof text != "object" && text != null )
+		if ( typeof text !== "object" && text != null )
 			return this.empty().append( (this[0] && this[0].ownerDocument || document).createTextNode( text ) );
 
 		var ret = "";
@@ -323,7 +323,7 @@
 	},
 
 	not: function( selector ) {
-		if ( selector.constructor == String )
+		if ( typeof selector === "string" )
 			// test special case where just one selector is passed in
 			if ( isSimple.test( selector ) )
 				return this.pushStack( jQuery.multiFilter( selector, this, true ) );
@@ -339,7 +339,7 @@
 	add: function( selector ) {
 		return this.pushStack( jQuery.unique( jQuery.merge(
 			this.get(),
-			typeof selector == 'string' ?
+			typeof selector === "string" ?
 				jQuery( selector ) :
 				jQuery.makeArray( selector )
 		)));
@@ -400,7 +400,7 @@
 			return undefined;
 		}
 
-		if( value.constructor == Number )
+		if ( typeof value === "number" )
 			value += '';
 
 		return this.each(function(){
@@ -550,7 +550,7 @@
 	var target = arguments[0] || {}, i = 1, length = arguments.length, deep = false, options;
 
 	// Handle a deep copy situation
-	if ( target.constructor == Boolean ) {
+	if ( typeof target === "boolean" ) {
 		deep = target;
 		target = arguments[1] || {};
 		// skip the boolean and the target
@@ -558,7 +558,7 @@
 	}
 
 	// Handle case when target is a string or something (possible in deep copy)
-	if ( typeof target != "object" && typeof target != "function" )
+	if ( typeof target !== "object" && !jQuery.isFunction(target) )
 		target = {};
 
 	// extend jQuery itself if only one argument is passed
@@ -579,7 +579,7 @@
 					continue;
 
 				// Recurse if we're merging object values
-				if ( deep && copy && typeof copy == "object" && !copy.nodeType )
+				if ( deep && copy && typeof copy === "object" && !copy.nodeType )
 					target[ name ] = jQuery.extend( deep, 
 						// Never move original objects, clone them
 						src || ( copy.length != null ? [ ] : { } )
@@ -599,7 +599,8 @@
 	// exclude the following css properties to add px
 	exclude = /z-?index|font-?weight|opacity|zoom|line-?height/i,
 	// cache defaultView
-	defaultView = document.defaultView || {};
+	defaultView = document.defaultView || {},
+	toString = Object.prototype.toString;
 
 jQuery.extend({
 	noConflict: function( deep ) {
@@ -611,19 +612,15 @@
 		return jQuery;
 	},
 
-	// See test/unit/core.js for details concerning this function.
+	// See test/unit/core.js for details concerning isFunction.
 	// Since version 1.3, DOM methods and functions like alert
 	// aren't supported. They return false on IE (#2968).
-	
-	// Memory leaks appear in IE6 when applying instanceof 
-	// to the window, document or any other COM object (#3485)
-	// http://ajaxian.com/archives/working-aroung-the-instanceof-memory-leak
-	isFunction: function( fn ) {
-		return !!fn && !!fn.hasOwnProperty && fn instanceof Function;
+	isFunction: function( obj ) {
+		return toString.call(obj) === "[object Function]";
 	},
-	
-	isArray: function( arr ){
-		return !!arr && arr.constructor == Array;
+
+	isArray: function( obj ) {
+		return toString.call(obj) === "[object Array]";
 	},
 
 	// check if an element is in a (or is an) XML document
@@ -761,7 +758,7 @@
 			value = value.call( elem, i );
 
 		// Handle passing in a number to a CSS property
-		return value && value.constructor == Number && type == "curCSS" && !exclude.test( name ) ?
+		return typeof value === "number" && type == "curCSS" && !exclude.test( name ) ?
 			value + "px" :
 			value;
 	},
@@ -946,19 +943,20 @@
 	clean: function( elems, context ) {
 		var ret = [];
 		context = context || document;
+
 		// !context.createElement fails in IE with an error but returns typeof 'object'
-		if (typeof context.createElement == 'undefined')
+		if ( typeof context.createElement === "undefined" )
 			context = context.ownerDocument || context[0] && context[0].ownerDocument || document;
 
 		jQuery.each(elems, function(i, elem){
-			if ( typeof elem == 'number' )
+			if ( typeof elem === "number" )
 				elem += '';
 
 			if ( !elem )
 				return;
 
 			// Convert html string into DOM nodes
-			if ( typeof elem == "string" ) {
+			if ( typeof elem === "string" ) {
 				// Fix "XHTML"-style tags in all browsers
 				elem = elem.replace(/(<(\w+)[^>]*?)\/>/g, function(all, front, tag){
 					return tag.match(/^(abbr|br|col|img|input|link|meta|param|hr|area|embed)$/i) ?
@@ -1139,7 +1137,7 @@
 		if( array != null ){
 			var i = array.length;
 			// The window, strings (and functions) also have 'length'
-			if( i == null || typeof array == 'string' || jQuery.isFunction(array) || array.setInterval )
+			if( i == null || typeof array === "string" || jQuery.isFunction(array) || array.setInterval )
 				ret[0] = array;
 			else
 				while( i )
@@ -1369,7 +1367,7 @@
 					(this.length ? jQuery.css( this[0], type ) : null) :
 
 					// Set the width or height on the element (default to pixels if value is unitless)
-					this.css( type, size.constructor == String ? size : size + "px" );
+					this.css( type, typeof size === "string" ? size : size + "px" );
 	};
 });
 
Index: src/fx.js
===================================================================
--- src/fx.js	(revision 5946)
+++ src/fx.js	(working copy)
@@ -117,7 +117,7 @@
 			type = "fx";
 		}
 
-		if ( !type || (typeof type == "string" && !fn) )
+		if ( !type || (typeof type === "string" && !fn) )
 			return queue( this[0], type );
 
 		return this.each(function(){
@@ -201,14 +201,14 @@
 jQuery.extend({
 
 	speed: function(speed, easing, fn) {
-		var opt = speed && speed.constructor == Object ? speed : {
+		var opt = typeof speed === "object" ? speed : {
 			complete: fn || !fn && easing ||
 				jQuery.isFunction( speed ) && speed,
 			duration: speed,
-			easing: fn && easing || easing && easing.constructor != Function && easing
+			easing: fn && easing || jQuery.isFunction(easing) && easing
 		};
 
-		opt.duration = jQuery.fx.off ? 0 : typeof opt.duration == 'number' ? opt.duration :
+		opt.duration = jQuery.fx.off ? 0 : typeof opt.duration === "number" ? opt.duration :
 			jQuery.fx.speeds[opt.duration] || jQuery.fx.speeds._default;
 
 		// Queueing
Index: src/selector.js
===================================================================
--- src/selector.js	(revision 5946)
+++ src/selector.js	(working copy)
@@ -92,7 +92,7 @@
 
 	find: function( t, context ) {
 		// Quickly handle non-string expressions
-		if ( typeof t != "string" )
+		if ( typeof t !== "string" )
 			return [ t ];
 
 		// check to make sure context is a DOM element or a document
@@ -214,7 +214,7 @@
 						// Do a quick check for the existence of the actual ID attribute
 						// to avoid selecting by the name attribute in IE
 						// also check to insure id is a string to avoid selecting an element with the name of 'id' inside a form
-						if ( (jQuery.browser.msie||jQuery.browser.opera) && oid && typeof oid.id == "string" && oid.id != m[2] )
+						if ( (jQuery.browser.msie||jQuery.browser.opera) && oid && typeof oid.id === "string" && oid.id != m[2] )
 							oid = jQuery('[@id="'+m[2]+'"]', elem)[0];
 
 						// Do a quick check for node name (where applicable) so
@@ -391,10 +391,10 @@
 			// Otherwise, find the expression to execute
 			} else {
 				var fn = jQuery.expr[ m[1] ];
-				if ( typeof fn == "object" )
+				if ( typeof fn === "object" )
 					fn = fn[ m[2] ];
 
-				if ( typeof fn == "string" )
+				if ( typeof fn === "string" )
 					fn = eval("false||function(a,i){return " + fn + ";}");
 
 				// Execute it against the current filter
Index: src/event.js
===================================================================
--- src/event.js	(revision 5946)
+++ src/event.js	(working copy)
@@ -40,7 +40,7 @@
 			handle = jQuery.data(elem, "handle") || jQuery.data(elem, "handle", function(){
 				// Handle the second event of a trigger and when
 				// an event is called after a page has unloaded
-				if ( typeof jQuery != "undefined" && !jQuery.event.triggered )
+				if ( typeof jQuery !== "undefined" && !jQuery.event.triggered )
 					return jQuery.event.handle.apply(arguments.callee.elem, arguments);
 			});
 		// Add elem as a property of the handle function
@@ -99,7 +99,7 @@
 
 		if ( events ) {
 			// Unbind all events for the element
-			if ( types == undefined || (typeof types == "string" && types.charAt(0) == ".") )
+			if ( types == undefined || (typeof types === "string" && types.charAt(0) == ".") )
 				for ( var type in events )
 					this.remove( elem, type + (types || "") );
 			else {
Index: src/ajax.js
===================================================================
--- src/ajax.js	(revision 5946)
+++ src/ajax.js	(working copy)
@@ -3,7 +3,7 @@
 	_load: jQuery.fn.load,
 
 	load: function( url, params, callback ) {
-		if ( typeof url != 'string' )
+		if ( typeof url !== "string" )
 			return this._load( url );
 
 		var off = url.indexOf(" ");
@@ -24,7 +24,7 @@
 				params = null;
 
 			// Otherwise, build a param string
-			} else if( typeof params == 'object' ) {
+			} else if( typeof params === "object" ) {
 				params = jQuery.param( params );
 				type = "POST";
 			}
@@ -178,7 +178,7 @@
 			type = s.type.toUpperCase();
 
 		// convert data if not already a string
-		if ( s.data && s.processData && typeof s.data != "string" )
+		if ( s.data && s.processData && typeof s.data !== "string" )
 			s.data = jQuery.param(s.data);
 
 		// Handle JSONP Parameter Callbacks
@@ -490,7 +490,7 @@
 			data = s.dataFilter( data, type );
 
 		// The filter can actually parse the response
-		if( typeof data == 'string' ){
+		if( typeof data === "string" ){
 
 			// If the type is "script", eval it in global context
 			if ( type == "script" )