Differentiating between arrays and “hashes” in Javascript

Question

In order to make the syntax for one of my functions nicer, I need to be able to tell whether a specific parameter is an array or \"hash\" (which I know are just objects).

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Answer 1

I think the most elegant way is to simply use the instanceof operator:

if (myVar instanceof Array)
    doSomething();

examples:

[] instanceof Array           // true
{} instanceof Array           // false
{length:100} instanceof Array // false
null instanceof Array         // false

Edit:

Be aware that it will fail when testing an object from another iFrame (see answers by @galambalazs and @bobince)