Make U.isArray() more reliable (multi-frame context)

[exside]

The problems with using instanceof Array arises when it comes to scripting in multi-frame DOM environments. In a nutshell, Array objects created within one iframe do not share [[Prototype]]’s with arrays created within another iframe. Their constructors are different objects and so both instanceof and constructor checks fail. The proposed solution is not dependent on frames (since it checks internal [[Class]]) and is more robust than duck-typing approach (e.g. checking for Prototype methods like .slice() that are unique to the Prototye).

Great writeup here: http://perfectionkills.com/instanceof-considered-harmful-or-how-to-write-a-robust-isarray/

PS: not sure which branch to target, can change if v3.0.1 is the wrong one!

[petersirka]

Hi @exside, thank you very much.

I don't agree because:

• first of all, Node.js doesn't contain iframes
• I didn't have any similar problem with checking Array type for more than 5 years
• your solution is slower:

I think that the current solution is very good.