optional chaining: error in summary?

The Summary section of page https://javascript.info/optional-chaining reads:

1. obj?.prop – returns obj.prop if obj exists, otherwise undefined.
   

2. obj?.[prop] – returns obj[prop] if obj exists, otherwise undefined.
   

3. obj.method?.() – calls obj.method() if obj.method exists, otherwise returns undefined.
   

but it seems that the first 2 lines should rather say:

1. ... obj.prop if obj.prop exists...
2. ...obj[prop] if obj[prop] exists...
   => actually in both cases when obj does not exist, as explained before in the chapter, it will throw an error.

打开链接的 javascript.info 页面中的 optional chaining 章节，并将 Summary 中的表述与前面对属性和方法访问的解释进行比较。如果该解释确认了所报告的区别，请更新 Summary 中的两条项目符号，然后检查渲染后的页面，确保 Summary 准确且清晰。