I try this code:
Code:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
    <title></title>
    <link rel="stylesheet" type="text/css" href="../Ext4/resources/css/ext-all.css"/>    
    <script type="text/javascript" src="../Ext4/bootstrap.js"></script>
    <style type="text/css">
    </style>
</head>
<body>    
    <div id="panel1"></div>
    <script type="text/javascript">

        Ext.onReady(function(){
            if(Ext.BLANK_IMAGE_URL.substr(0,4)!="data"){                
                Ext.BLANK_IMAGE_URL="./images/s.gif";
            }
            
            var panel=Ext.create("Ext.Panel",{
                renderTo:"panel1",
                layout:"auto",
                height:500,
                width:400,
                tbar:[
                    {text:"Load",scope:panel,handler:function(){
                        console.log(panel.loader)
                    }}
                ]
            });
        
            
        });
    </script>
</body>
</html>
Show in the Console:null

So I modified the definition of the panel:
Code:
            var panel=Ext.create("Ext.Panel",{
                renderTo:"panel1",
                layout:"auto",
                height:500,
                width:400,
                autoLoad:"c.js",
                renderer:"component",
                tbar:[
                    {text:"Load",scope:panel,handler:function(){
                        console.log(panel.loader)
                    }}
                ]
            });
The code in c.js:
Code:
{xtype:'panel',height:100,width:200,html:"Hello world"}
The c.js loader,but it is rendering html, but not Componet(renderer:"component",).