new String("a") == new String("a") is false???

[cezarneaga]

hi Dan,

love how you explain weird things simply. could you give this a try?

why is new String("a") == new String("a") false? same with all primitives... ref: http://www.ecma-international.org/ecma-262/5.1/#sec-11.9.3 NOTE 3 for example.

thanks! Cezar

[Youmoo]

My understanding:

1. new always returns a newly created object, and thus typeof new String('a') === 'object'. reference
2. x==y returns true if x and y refer to the same object. Otherwise, return false.Reference:1.f.

In your example new String("a") == new String("a"), new called twice, so two distinct objects are created , so false returned.

Sorry for my not-so-good English.

[cezarneaga]

thanks @Youmoo ! your english is excellent. don't apologise. no need. :)

that's what i need the explanation for. the distinct objects are the same except the reference the compiler gives it? where does the reference lie in? in global scope? how does the engine know its different. where is the compiler looking to tell its a different one? is the compiler checking the reference only? is there a way to look the reference up?

why doesnt it coerce ?

i guess its more of a philosophical question :)

[srobinson]

Hi @cezarneaga - in chrome V8 this is achieved using hidden classes and inline caches. This is an excellent talk:

https://www.youtube.com/watch?v=FrufJFBSoQY