diff --git a/lib/dom.js b/lib/dom.js
index 0bc123eaf..30c063a81 100644
--- a/lib/dom.js
+++ b/lib/dom.js
@@ -63,7 +63,7 @@ function arrayIncludes (list) {
 }
 
 function copy(src,dest){
-	for(var p in src){
+	for(var p of Object.keys(src)){
 		dest[p] = src[p];
 	}
 }
@@ -552,7 +552,7 @@ Node.prototype = {
     		var map = el._nsMap;
     		//console.dir(map)
     		if(map){
-    			for(var n in map){
+    			for(var n of Object.keys(map)){
     				if(map[n] == namespaceURI){
     					return n;
     				}
@@ -569,7 +569,7 @@ 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] ;
     			}
     		}
@@ -1608,7 +1608,7 @@ 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){
+	for(var n of Object.keys(node)){
 		var v = node[n];
 		if(typeof v != 'object' ){
 			if(v != node2[n]){
diff --git a/lib/sax.js b/lib/sax.js
index 48d8cfe46..3100dd9b7 100644
--- a/lib/sax.js
+++ b/lib/sax.js
@@ -142,7 +142,7 @@ function parse(source,defaultNSMapCopy,entityMap,domBuilder,errorHandler){
 		        if(endIgnoreCaseMach){
 		        	domBuilder.endElement(config.uri,config.localName,tagName);
 					if(localNSMap){
-						for(var prefix in localNSMap){
+						for(var prefix of Object.keys(localNSMap)){
 							domBuilder.endPrefixMapping(prefix) ;
 						}
 					}
@@ -493,7 +493,7 @@ function appendElement(el,domBuilder,currentNSMap){
 	if(el.closed){
 		domBuilder.endElement(ns,localName,tagName);
 		if(localNSMap){
-			for(prefix in localNSMap){
+			for(prefix of Object.keys(localNSMap)){
 				domBuilder.endPrefixMapping(prefix)
 			}
 		}
@@ -537,7 +537,7 @@ function fixSelfClosed(source,elStartEnd,tagName,closeMap){
 	//}
 }
 function _copy(source,target){
-	for(var n in source){target[n] = source[n]}
+	for(var n of Object.keys(source)){target[n] = source[n]}
 }
 function parseDCC(source,start,domBuilder,errorHandler){//sure start with '<!'
 	var next= source.charAt(start+2)