JavaScript判断对象是否为空
https://blog.csdn.net/weixin_44019523/article/details/113869190?utm_term=js%E5%88%A4%E6%96%AD%E9%9B%86%E5%90%88%E4%B8%8D%E4%B8%BA%E7%A9%BA&utm_medium=distribute.pc_aggpage_search_result.none-task-blog-2~all~sobaiduweb~default-1-113869190&spm=3001.4430