diff --git a/lib/chrome.js b/lib/chrome.js
index fa67f2b..874dbb4 100644
--- a/lib/chrome.js
+++ b/lib/chrome.js
@@ -926,11 +926,16 @@ var ChromeObject = function() {
     this.traceMouseClick = function() {
         return this.evaluate('window.addEventListener("click",function(e){var t=e.clientX,n=e.clientY,l=document.createElement("div");l.style.position="absolute",l.style.width="20px",l.style.height="20px",l.style.backgroundColor="#00ff00",l.style.zIndex=99999,l.style.top=window.pageYOffset+n-10+"px",l.style.left=window.pageXOffset+t-10+"px",document.body.appendChild(l)});');
     };
-    
+
     this.getWindowInnerHeight = function() {
         return this.getEvaluatedValue('window.innerHeight');
     };
 
+    // formula: y > 0 and y + h < ih
+    this.isVisibleElementInViewport = function(elementPosition) {
+        return (elementPosition.y > 0 && (elementPosition.y + elementPosition.h < this.getWindowInnerHeight());
+    };
+
     this.create();
 };