extjs: make textfield 100% width

new Ext.FormPanel({
    labelWidth: 75,
    autoWidth: true,
    items: [
        {
            xtype: 'textfield',
            fieldLabel:'Name',
            anchor:'100%' // anchor : 'width height' exemple: anchor:'100% 98%' or anchor:'-29 -10'(bodycontentwidth - 29, bodycontentheight - 10) 
        }]
}

• Note:
  1. Set autoWidth: true in the container
  2. Set anchor: 100%