layui iframe弹出层高度自适应

layer.open({
    type: 2,
    title: "弹出层标题",
    area: '800px',
    shadeClose: true,
    btn: ['确定', '取消'],
    success: function(layero, index){
        layer.iframeAuto(index)
    },
    content: 'xxx'
});