ext表单提交出错，求大神帮助

前台页面代码如下：
 <%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>用户注册</title>
    <link href="./ext/resources/css/ext-all.css" type="text/css" rel="stylesheet">
    <script type="text/javascript" src="./ext/adapter/ext/ext-base.js"></script>
    <script type="text/javascript" src="./ext/ext-all.js"></script>
    <script type="text/javascript">
        Ext.onReady(function(){
            var myForm=new Ext.FormPanel({
                frame:true,
                id:'myForm',
                renderTo:Ext.getBody(),
                title:'用户注册',
                style:'margin-right:auto;margin-left:auto;margin-top:8px;',
                labelAlign:'right',
                buttonAlign:'center',
                width:400,
                height:200,
                items:[{
                    xtype:'textfield',
                    fieldLabel:'用户名',
                    name:'username',
                    allowBlank:false,
                    blankText:'用户名不能为空',
                    id:'username'
                },
                {
                    xtype:'textfield',
                    fieldLabel:'密码',
                    name:'password',
                    allowBlank:false,
                    blankText:'密码不能为空',
                    id:'password'
                },
                {
                    xtype:'textfield',
                    fieldLabel:'年龄',
                    name:'age',
                    allowBlank:false,
                    blankText:'年龄不能为空',
                    id:'age'
                },
                {
                    xtype:'textfield',
                    fieldLabel:'性别',
                    id:'gender',
                    name:'gender',
                    allowBlank:false,
                    blankText:'性别不能为空'
                }],
                buttons:[{
                    text:'注册',
                    type:'submit',
                    id:'regist',
                    handler:regist
                },
                {
                    text:'重置',
                    handler:function(){
                        myForm.getForm().reset();
                    }
                }]
            })
        })      
        function regist(){
            var username=document.getElementById("username").value;
            var password=document.getElementById("password").value;
            var age=document.getElementById("age").value;
            var gender=document.getElementById("gender").value;
            myForm.getForm().submit({
                url:'http://localhost:8080/ssi-test2/regist.action',
                params:{"username":username,"password":password,"age":age,"gender":gender},
                method:'post',
                success:function(form,action){
                    var status=action.result.status;
                    if(status==1){
                        window.location.href="login.jsp"
                    }else{
                        var msg=action.result.msg;
                        Ext.Msg.alert("提示",msg)
                    }
                },
                failure:function(form,action){
                    myForm.getForm().reset()
                }
            })
        }
    </script>
</head>
<body>
</body>
</html>
报错如下：TypeError: myForm.getForm is not a function
var myForm=new Ext.FormPanel({
改为
window.myForm=new Ext.FormPanel({
作为全局变量，要不你的那个regist函数中访问不到