diff --git a/paper-datatable-card.html b/paper-datatable-card.html
index f85e36d..2f4b894 100644
--- a/paper-datatable-card.html
+++ b/paper-datatable-card.html
@@ -433,12 +433,18 @@
 								var done = function(){
 									i++;
 									if(i == 2){
-										var sortedItems = ids.map((id) => items.find((item) => item[this.idProperty] == id));
+										var sortedItems = ids.map(function (id) {
+											return items.find(function (item) {
+												return item[undefined.idProperty] == id;
+											});
+										});
 										processItems(sortedItems);
 									}
 								}.bind(this);
 
-								var idsInCache = ids.filter((id) => this._cache.has(id));
+								var idsInCache = ids.filter(function (id) {
+									return undefined._cache.has(id);
+								});
 								if(idsInCache.length){
 									var cacheItems = [];
 									idsInCache.forEach(function(id){
@@ -450,7 +456,9 @@
 									done();
 								}
 
-								var idsNotInCache = ids.filter((id) => !this._cache.has(id));
+								var idsNotInCache = ids.filter(function (id) {
+									return !undefined._cache.has(id);
+								});
 								if(idsNotInCache.length){
 									this.dataSource.getByIds(idsNotInCache).then(function(newItems){
 										items = items.concat(newItems);
diff --git a/paper-datatable.html b/paper-datatable.html
index 27caf54..d8778d3 100644
--- a/paper-datatable.html
+++ b/paper-datatable.html
@@ -1021,13 +1021,13 @@
 						// see: console.log(this._columns.length);
 
 						var ths = Polymer.dom(this.root).querySelectorAll('th');
-						ths.forEach((th) => {
-							if(th.dataColumn){
+						ths.forEach(function (th) {
+							if (th.dataColumn) {
 								console.dir(th);
 								var column = th.dataColumn;
-								if(th.scrollWidth > th.offsetWidth){
+								if (th.scrollWidth > th.offsetWidth) {
 									column.set('tooltip', column.header);
-								}else{
+								} else {
 									column.set('tooltip', '');
 								}
 							}