js 对象是否存在判断

复制代码 代码如下:

  <html>

  <head>

  <meta http-equiv="Content-Type" content="text/html; charset=gb2312">

  <title>javascript object</title>

  <body>

  <input id="aaa">

  <input type=button onclick="check('aaa')" value="checkaaa">

  <input type=button onclick="check('aaffdssfg')" value="checkother">

  <script language="javascript">

  <!--

  function check(strObj)

  {

  if(typeof(eval("document.all."+strObj))!= "undefined")

  {

  alert(strObj +" is an object");

  }

  else

  {

  alert(strObj +" is not an object");

  }

  }

  //-->

  </script>

  </body>