diff --git a/lib/dom.js b/lib/dom.js
index 633c34290..c6ebfe95d 100644
--- a/lib/dom.js
+++ b/lib/dom.js
@@ -62,7 +62,9 @@ function arrayIncludes (list) {
 
 function copy(src,dest){
 	for(var p in src){
-		dest[p] = src[p];
+		if (Object.prototype.hasOwnProperty.call(src, p)) {
+			dest[p] = src[p];
+		}
 	}
 }
 
@@ -509,9 +511,9 @@ Node.prototype = {
     		//console.dir(map)
     		if(map){
     			for(var n in map){
-    				if(map[n] == namespaceURI){
-    					return n;
-    				}
+						if (Object.prototype.hasOwnProperty.call(map, n) && map[n] === namespaceURI) {
+							return n;
+						}
     			}
     		}
     		el = el.nodeType == ATTRIBUTE_NODE?el.ownerDocument : el.parentNode;
@@ -525,7 +527,7 @@ Node.prototype = {
     		var map = el._nsMap;
     		//console.dir(map)
     		if(map){
-    			if(prefix in map){
+    			if(Object.prototype.hasOwnProperty.call(map, prefix)){
     				return map[prefix] ;
     			}
     		}
@@ -1424,11 +1426,13 @@ function importNode(doc,node,deep){
 //					attributes:1,childNodes:1,parentNode:1,documentElement:1,doctype,};
 function cloneNode(doc,node,deep){
 	var node2 = new node.constructor();
-	for(var n in node){
-		var v = node[n];
-		if(typeof v != 'object' ){
-			if(v != node2[n]){
-				node2[n] = v;
+	for (var n in node) {
+		if (Object.prototype.hasOwnProperty.call(node, n)) {
+			var v = node[n];
+			if (typeof v != "object") {
+				if (v != node2[n]) {
+					node2[n] = v;
+				}
 			}
 		}
 	}
diff --git a/lib/sax.js b/lib/sax.js
index b706ef1af..0764523fb 100644
--- a/lib/sax.js
+++ b/lib/sax.js
@@ -135,8 +135,10 @@ function parse(source,defaultNSMapCopy,entityMap,domBuilder,errorHandler){
 		        if(endIgnoreCaseMach){
 		        	domBuilder.endElement(config.uri,config.localName,tagName);
 					if(localNSMap){
-						for(var prefix in localNSMap){
-							domBuilder.endPrefixMapping(prefix) ;
+						for (var prefix in localNSMap) {
+							if (Object.prototype.hasOwnProperty.call(localNSMap, prefix)) {
+								domBuilder.endPrefixMapping(prefix);
+							}
 						}
 					}
 					if(!endMatch){
@@ -478,8 +480,10 @@ function appendElement(el,domBuilder,currentNSMap){
 	if(el.closed){
 		domBuilder.endElement(ns,localName,tagName);
 		if(localNSMap){
-			for(prefix in localNSMap){
-				domBuilder.endPrefixMapping(prefix)
+			for (prefix in localNSMap) {
+				if (Object.prototype.hasOwnProperty.call(localNSMap, prefix)) {
+					domBuilder.endPrefixMapping(prefix);
+				}
 			}
 		}
 	}else{
@@ -525,9 +529,15 @@ function fixSelfClosed(source,elStartEnd,tagName,closeMap){
 	return pos<elStartEnd;
 	//}
 }
-function _copy(source,target){
-	for(var n in source){target[n] = source[n]}
+
+function _copy (source, target) {
+	for (var n in source) {
+		if (Object.prototype.hasOwnProperty.call(source, n)) {
+			target[n] = source[n];
+		}
+	}
 }
+
 function parseDCC(source,start,domBuilder,errorHandler){//sure start with '<!'
 	var next= source.charAt(start+2)
 	switch(next){