html5 - Get updated value of a text area - javascript -

how value after updating text area in javascript?

document.getelementbyid("txtarea").innerhtml doest give updated value.

<p>     <textarea style="width:270px;height:100px" id='txtdata' rows='3' cols='80'></textarea> </p> <p>     <button type=button style="width:270px;height:40px" onclick="getvalue();" id='btnget'>get</button> </p>   <script type="text/javascript"> function getvalue () {         alert(document.getelementbyid("txtdata").innerhtml);     } </script> 

thanks in advance.

document.getelementbyid("txtarea").value; //value of textarea