可以在JavaScript中创建对对象外部代码只读的属性吗？

Question

在JavaScript中，是否可以存在某些属性，使得它们只能由其附加到的对象内部的代码修改，并且是只读的，并且可以防止其对象外部的代码删除它们？

Answer 1

Yes, one possibility is to use the revealing module pattern - keep the variables that you want to keep private and unalterable inside the module, and expose a getter that returns that variable. See comments:

 const counter = (() => { let num = 5; return { get num() { return num }, increment: () => num++, }; })(); console.log(counter.num); // 5 counter.num++; // Won't do anything, since num can only be changed from the inside console.log(counter.num); // Still 5 counter.increment(); // Calls the method internal to the object, which increments num console.log(counter.num); // 6