billboard is not define

毕设

vue.runtime.esm.js?c320:619 [Vue warn]: Property or method "billboard" is not defined on the instance but referenced during render. Make sure that this property is reactive, either in the data option, or for class-based components, by initializing the property. See: https://vuejs.org/v2/guide/reactivity.html#Declaring-Reactive-Properties.

不知道怎么定义
显示billboard这个框

是不是忘了把函数initHistoryData()和getViewExtend()放到methods:｛｝中。
可以参考下这篇文章，希望对你有帮助：

[Vue warn]: Property or method “getViewExtend“ is not defined on the instance but referenced during_晚秋的专栏-CSDN博客 报错：[Vue warn]: Property or method "getViewExtend" is not defined on the instance but referenced during render. Make sure that this property is reactive, either in the data option, or for class-based components, by initializing the property. See: https://v. https://blog.csdn.net/chenguizhenaza/article/details/116739971?spm=1001.2014.3001.5501