Why does typeof val === 'object' && val.constructor === Array fail if val created in other frame?

Asked Mar 06 '13 at 01:35

Active Feb 20 '15 at 01:55

Viewed 312 times

Quoting Crockford in JavaScript The Good Parts:

We can ... define our own is_array function:

var is_array = function (value) {
    return value && typeof value === 'object' && value.constructor === Array;
}

Unfortunately, it fails to identify arrays that were constructed in a different Windows or frame.

And then he doesn't explain why. So! Why?

edited Feb 20 '15 at 01:55

Kevin Brown-Silva

asked Mar 06 '13 at 01:35

djechlin

5

I believe it is the third condition that fails. Since each `window.Array !== otheframe.Array`. – Paul Mar 06 '13 at 01:39
@ExplosionPills - So is the gist that a non-frame window's Array constructor is not the same as one from a frame (iframe)? Or that *every* frame's Array constructor is specific to that frame? – Jared Farrish Mar 06 '13 at 01:44
1

@JaredFarrish *every* frame has its own constructor – Explosion Pills Mar 06 '13 at 01:50
@ExplosionPills - Hmm. I wonder why... `:P` – Jared Farrish Mar 06 '13 at 01:54
@ExplosionPills - That was going to be my guess. Makes sense. – Jared Farrish Mar 06 '13 at 02:03

0 Answers0