js打印div指定区域内容

<script>
function myPrint(obj){
    var newWindow=window.open("打印窗口","_blank");//打印窗口要换成页面的url
    var docStr = obj.innerHTML;
    newWindow.document.write(docStr);
    newWindow.document.close();
    newWindow.print();
    newWindow.close();
}
</script>
<div id="print">
<hr />
   打印演示区域,点击打印后会在新窗口加载这里的内容！
<hr />
</div>
<button onclick="myPrint(document.getElementById('print'))">打 印</button>