搶先讀了一下第一章，在講與 JS 相關的歷史，其中提到一段讓我很感興趣的議題：
As such, sometimes the JS engines will refuse to conform to a specification-dictated change because it would break that web content.
In these cases, often TC39 will backtrack and simply choose to conform the specification to the reality of the web. For example, TC39 planned to add a contains(…) method for Arrays, but it was found that this name conflicted with old JS frameworks still in use on some sites, so they changed the name to a non-conflicting includes(…). The same happened with a comedic/tragic JS community crisis dubbed “smooshgate”, where the planned flatten(…) method was eventually renamed flat(…).
大意是在說有時候 JS 的規格必須跟現實（已經存在的那些舊的實作）妥協。例如說原本 Array 要加上一個叫做 contains 的 method，但因為會有問題所以改叫 includes，flatten 也改名叫做 flat。