diff --git a/iscroll/iscroll-lite.d.ts b/iscroll/iscroll-lite.d.ts
index 085f844b0..f5c723c98 100644
--- a/iscroll/iscroll-lite.d.ts
+++ b/iscroll/iscroll-lite.d.ts
@@ -39,8 +39,9 @@ declare class iScroll {
 
     destroy(): void;
     refresh(): void;
-    scrollTo(x: number, y: number, time: number, relative: boolean): void;
-    scrollToElement(element: string, time: number): void;
+    scrollTo(x: number, y: number, time?: number, relative?: boolean): void;
+    scrollToElement(element: string, time?: number): void;
+    scrollToElement(element: HTMLElement, time?: number): void;
     disable(): void;
     enable(): void;
     stop(): void;
diff --git a/iscroll/iscroll-tests.ts b/iscroll/iscroll-tests.ts
index e8141d5ea..773b62acf 100644
--- a/iscroll/iscroll-tests.ts
+++ b/iscroll/iscroll-tests.ts
@@ -17,7 +17,15 @@ var myScroll4 = new iScroll('wrapper', {
 var myScroll6 = new iScroll('wrapper', { scrollbarClass: 'myScrollbar' });
 
 myScroll1.refresh();
+myScroll1.scrollTo(0, 100);
+myScroll1.scrollTo(0, 100, 200);
+myScroll1.scrollTo(0, 100, 200, true);
 
+myScroll1.scrollToElement('selectedElement');
+myScroll1.scrollToElement('selectedElement', 250);
+
+myScroll1.scrollToElement(document.getElementById('selectedElement'));
+myScroll1.scrollToElement(document.getElementById('selectedElement'), 250);
 
 var myScroll7 = new iScroll(document.getElementById('wrapper'));
 var myScroll8 = new iScroll(document.getElementById('wrapper'), { scrollbarClass: 'myScrollbar' });
\ No newline at end of file
diff --git a/iscroll/iscroll.d.ts b/iscroll/iscroll.d.ts
index 4c89038ed..379d7c456 100644
--- a/iscroll/iscroll.d.ts
+++ b/iscroll/iscroll.d.ts
@@ -64,12 +64,13 @@ declare class iScroll {
 
     destroy(): void;
     refresh(): void;
-    scrollTo(x: number, y: number, time: number, relative: boolean): void;
-    scrollToElement(element: string, time: number): void;
-    scrollToPage(pageX: number, pageY: number, time: number): void;
+    scrollTo(x: number, y: number, time?: number, relative?: boolean): void;
+    scrollToElement(element: string, time?: number): void;
+    scrollToElement(element: HTMLElement, time?: number): void;
+    scrollToPage(pageX: number, pageY: number, time?: number): void;
     disable(): void;
     enable(): void;
     stop(): void;
-    zoom(x: number, y: number, scale: number, time: number): void;
+    zoom(x: number, y: number, scale: number, time?: number): void;
     isReady(): boolean;
 }