diff --git a/chrome/content/zotero/xpcom/connector/translate_item.js b/chrome/content/zotero/xpcom/connector/translate_item.js
index 4f68dfdd6..febac63e2 100644
--- a/chrome/content/zotero/xpcom/connector/translate_item.js
+++ b/chrome/content/zotero/xpcom/connector/translate_item.js
@@ -57,7 +57,7 @@ Zotero.Translate.ItemSaver.prototype = {
 	 */
 	"_saveToServer":function(items, callback) {
 		var newItems = [];
-		for(var i in items) {
+		for(var i=0, n=items.length; i<n; i++) {
 			newItems.push(Zotero.Utilities.itemToServerJSON(items[i]));
 		}
 		
diff --git a/chrome/content/zotero/xpcom/date.js b/chrome/content/zotero/xpcom/date.js
index 0d88fb384..19846b818 100644
--- a/chrome/content/zotero/xpcom/date.js
+++ b/chrome/content/zotero/xpcom/date.js
@@ -344,7 +344,7 @@ Zotero.Date = new function(){
 			if (Zotero.locale != 'en-US') {
 				Zotero.Date.getMonths();
 				months = months.concat(_months['short']).concat(_months['long']);
-				for(var i in months) months[i] = months[i].toLowerCase();
+				for(var i=0, n=months.length; i<n; i++) months[i] = months[i].toLowerCase();
 			}
 			
 			if(!_monthRe) {
diff --git a/chrome/content/zotero/xpcom/translation/translate.js b/chrome/content/zotero/xpcom/translation/translate.js
index 356d37a61..129283b0c 100644
--- a/chrome/content/zotero/xpcom/translation/translate.js
+++ b/chrome/content/zotero/xpcom/translation/translate.js
@@ -825,7 +825,7 @@ Zotero.Translate.Base.prototype = {
 				args.push(arguments[i]);
 			}
 			
-			for(var i in this._handlers[type]) {
+			for(var i=0, n=this._handlers[type].length; i<n; i++) {
 				Zotero.debug("Translate: Running handler "+i+" for "+type, 5);
 				try {
 					returnValue = this._handlers[type][i].apply(null, args);
@@ -891,7 +891,7 @@ Zotero.Translate.Base.prototype = {
 		this._properToProxyFunctions = properToProxyFunctions ? properToProxyFunctions : null;
 		this._waitingForRPC = false;
 		
-		for(var i in allPotentialTranslators) {
+		for(var i=0, n=allPotentialTranslators.length; i<n; i++) {
 			var translator = allPotentialTranslators[i];
 			if(translator.runMode === Zotero.Translator.RUN_MODE_IN_BROWSER) {
 				this._potentialTranslators.push(translator);
@@ -1202,7 +1202,7 @@ Zotero.Translate.Base.prototype = {
 		"Zotero.Item = function (itemType) {"+
 				"const createArrays = "+createArrays+";"+
 				"this.itemType = itemType;"+
-				"for(var i in createArrays) {"+
+				"for(var i=0, n=createArrays.length; i<n; i++) {"+
 					"this[createArrays[i]] = [];"+
 				"}"+
 		"};";
@@ -1454,7 +1454,7 @@ Zotero.Translate.Web.prototype._translateRPCComplete = function(obj, failureCode
 		);
 	} else {
 		// if we don't have to select items, continue
-		for(var i in obj.items) {
+		for(var i=0, n=obj.items.length; i<n; i++) {
 			this._runHandler("itemDone", null, obj.items[i]);
 		}
 		this.newItems = obj.items;
@@ -1815,7 +1815,7 @@ Zotero.Translate.Search.prototype.setTranslator = function(translator) {
 		
 		// accept a list of objects
 		this.translator = [];
-		for(var i in translator) {
+		for(var i=0, n=translator.length; i<n; i++) {
 			this.translator.push(translator[i]);
 		}
 		return true;
diff --git a/chrome/content/zotero/xpcom/utilities.js b/chrome/content/zotero/xpcom/utilities.js
index d403d452c..95029659f 100644
--- a/chrome/content/zotero/xpcom/utilities.js
+++ b/chrome/content/zotero/xpcom/utilities.js
@@ -719,6 +719,8 @@ Zotero.Utilities = {
 	"deepCopy":function(obj) {
 		var obj2 = (obj instanceof Array ? [] : {});
 		for(var i in obj) {
+			if(!obj.hasOwnProperty(i)) continue;
+			
 			if(typeof obj[i] === "object") {
 				obj2[i] = Zotero.Utilities.deepCopy(obj[i]);
 			} else {
@@ -813,7 +815,7 @@ Zotero.Utilities = {
 		if(!(elements instanceof Array)) elements = [elements];
 		
 		var results = [];
-		for(var i in elements) {
+		for(var i=0, n=elements.length; i<n; i++) {
 			var element = elements[i];
 			
 			// Firefox 5 hack, so we will preserve Fx5DOMWrappers
@@ -861,7 +863,7 @@ Zotero.Utilities = {
 		if(!elements.length) return null;
 		
 		var strings = new Array(elements.length);
-		for(var i in elements) {
+		for(var i=0, n=elements.length; i<n; i++) {
 			strings[i] = elements[i].textContent;
 		}