JS中遍历table及判断对象非空、未定义

var tbobj=document.getElementById(autoTableId);
 for(var i=0;i<tbobj.rows.length;i++){
  var  trobj = tbobj.rows[i];
  for(var j=0;j<trobj.cells.length;j++){
    var tdobj = trobj.cells[j];
   for(var k=0;k<tdobj.childNodes.length;k++){
    var childNode = tdobj.childNodes[k];
    if( typeof(childNode.name)!= "undefined" ){
     alert(childNode.name);
    }  
   }
  }  
 }

 

ps：JS中判断对象非空，应为if(object)或if(!object);不应该if(object != null),这是错的~

判断对象未定义为：if( typeof(object)!= "undefined" ){}