I find this easier to understand with a visualization. Here I’m using purple ovals for calls to node, green rectangles for calls to cons, black ovals for calls to empty and black rectangles for calls to nil:
Creating custom commands
。关于这个话题，wps提供了深入分析
这个项目从去年上半年就开始酝酿，内部被列为「最高优先级绝密项目」。。关于这个话题，谷歌提供了深入分析
if !groups.has(s.grade) {