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.

開啟連結的 javascript.info 頁面中的 optional chaining 章節，並將 Summary 中的措辭與前面對屬性和方法存取的說明進行比較。如果該說明確認了所回報的差異，請更新 Summary 中的兩個項目符號，然後檢查轉譯後的頁面，確保 Summary 正確且清楚。