title: Exception: java.lang.NullPointerException
body: <p>I am using the following code to verify whether the image has loaded completely on a webpage or not.</p>
  
  <pre><code>public static boolean IsImageVisible1(WebDriver driver, By locator)
    {
      WebElement image = driver.findElement(locator);
      //if the element not present you'll get the NoSuchElementException exception
      JavascriptExecutor js = (JavascriptExecutor) driver;
      boolean imageLoaded1  = (boolean) js.executeScript("return arguments[0].complete &amp;&amp; (typeof arguments[0].naturalWidth !== \"undefined\") &amp;&amp; (arguments[0].naturalWidth &gt; 0)", image);      
      return imageLoaded1;
    }
  </code></pre>
  
  <p>while running this method i am getting following exception </p>
  
  <pre><code>java.lang.NullPointerException
  at pack2.image.IsImageVisible1(image.java:58)
  at pack2.image.test(image.java:23)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
  at java.lang.reflect.Method.invoke(Unknown Source)
  at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
  at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
  at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
  at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
  at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
  at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
  at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
  at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
  at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
  at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
  at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
  at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
  at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
  at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
  at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
  at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
  at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
  at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
  at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
  
  
  function call to above method: IsImageVisible1(driver, By.id("homepage-preview"));
  </code></pre>
  
  <p>let me know what i am missing in the above javascript code. </p>
  
  <p>Thanks in advance</p>