在ES5 / 6中，javascript属性名称如“__proto__”是否未标准化？

Question

There're some properties in js starts/ends with double underscores like proto . But I know it equals to constructor.prototype, right? I wish to know whether ES5/ES6 standard included these xxx_ property names, or they're just implementation specific keywords, might have different behavior in different implementations?

Plus: where can I check if a keyword is part of ES stardard, any recommended web-sites?

Thanks.

Answer 1

I know it equals to constructor.prototype, right?

No .

I wish to know whether ES5/ES6 standard included these __xxx__ property names, or they're just implementation specific keywords, might have different behavior in different implementations?

You can find an overview in the MDN documentation , there are __count__ , __noSuchMethod__ , __parent__ , __proto__ , __defineGetter__ , __defineSetter__ , __lookupGetter__ , and __lookupSetter__ ; and all of them are deprecated . Other implementations than Gecko might have featured more.

Only the getter/setter methods and __proto__ were common amongst implementations, and only __proto__ got into the compatibilty section of the ES6 standard .

where can I check if a keyword is part of ES stardard, any recommended web-sites?

Just read the standards themselves !