ExtJs - Basic form:可以将params key设置为变量吗？

var key = 'username';  // 可以将params key设置为变量

Ext.create('Ext.form.Panel', {
    title: 'Basic Form',
    bodyPadding: 5,
    width: 300,

    items: [{
        xtype: 'textfield',
        fieldLabel: 'Username',
        name: key,  // 将params key设置为变量
        allowBlank: false
    }],

    buttons: [{
        text: 'Submit',
        handler: function() {
            var form = this.up('form').getForm();
            if (form.isValid()) {
                form.submit({
                    url: 'save.php',
                    success: function(form, action) {
                        Ext.Msg.alert('Success', action.result.msg);
                    },
                    failure: function(form, action) {
                        Ext.Msg.alert('Failed', action.result.msg);
                    }
                });
            }
        }
    }],
    renderTo: Ext.getBody()
});