function getClipboard() {
   if (window.clipboardData) {
      return(window.clipboardData.getData('Text'));
   }
   else if (window.netscape) {
      netscape.security.PrivilegeManager.enablePrivilege('UniversalXPConnect');
      var clip = Components.classes['@mozilla.org/widget/clipboard;1'].createInstance(Components.interfaces.nsIClipboard);
      if (!clip) return;
      var trans = Components.classes['@mozilla.org/widget/transferable;1'].createInstance(Components.interfaces.nsITransferable);
      if (!trans) return;
      trans.addDataFlavor('text/unicode');
      clip.getData(trans,clip.kGlobalClipboard);
      var str = new Object();
      var len = new Object();
      try {
         trans.getTransferData('text/unicode',str,len);
      }
      catch(error) {
         return null;
      }
      if (str) {
         if (Components.interfaces.nsISupportsWString) str=str.value.QueryInterface(Components.interfaces.nsISupportsWString);
         else if (Components.interfaces.nsISupportsString) str=str.value.QueryInterface(Components.interfaces.nsISupportsString);
         else str = null;
      }
      if (str) {
         return(str.data.substring(0,len.value / 2));
      }
   }
   return null;
}

function test()
{
   var str=getClipboard();
   if(str!=null)
   {
        var list=str.split(" ");
        if(list.length>3)
        {
            document.getElementById("TextBox1").value=list[0];
            document.getElementById("TextBox2").value=list[1];
            document.getElementById("TextBox3").value=list[2];
            document.getElementById("TextBox4").value=list[3];
        }
   }
}

------解决方案--------------------
 var list=str.split(" ");
------------------------------
上面的split自己写一个分割字符串的函数，然后添加到var list=new Array();中