print function for particular div in js

function printDiv(divName) {
     var printContents = document.getElementById(divName).innerHTML;
     var originalContents = document.body.innerHTML;

     document.body.innerHTML = printContents;

     window.print();

     document.body.innerHTML = originalContents;
}

<div id="printableArea">
      <h1>Print me</h1>
</div>

<input type="button" onclick="printDiv('printableArea')" value="print a div!" />