what is NaN, Object or primitive?
NaN - Not a Number
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NaN is a property of the Number class – May 08 '12 at 12:23
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1`typeof NaN == "number"` – Michael Berkowski May 08 '12 at 12:23
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1NaN is like NULL. you can refer this [SO Post][1] [1]: http://stackoverflow.com/questions/559792/what-is-the-reserved-keyword-for-nan-in-javascript – avani gadhai May 08 '12 at 12:28
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1@rsplak: `NaN` is also a property of the global object, both have the value `NaN`. – Andy E May 08 '12 at 12:30
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1Have a look at the specification [here](http://es5.github.com/#x8.5) and [here](http://es5.github.com/#x15.1.1.1) for more information about `NaN`. – Felix Kling May 08 '12 at 12:42
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@avanigadhai Not exactly. `null` is actually a type, with only one value: `null`. – kapa May 08 '12 at 13:33
3 Answers
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It's a primitive. You can check in a number of ways:
typeof NaNgives "number," not "object."Add a property, it disappears.
NaN.foo = "hi"; console.log(NaN.foo) // undefinedNaN instanceof Numbergives false (but we know it's a number, so it must be a primitive).
It wouldn't really make sense for NaN to be an object, because expressions like 0 / 0 need to result in NaN, and math operations always result in primitives. Having NaN as an object would also mean it could not act as a falsey value, which it does in some cases.
Dagg Nabbit
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NaN is a property of the global object.
The initial value of NaN is Not-A-Number — the same as the value of Number.NaN. In modern browsers, NaN is a non-configurable, non-writable property. Even when this is not the case, avoid overriding it.
It is rather rare to use NaN in a program. It is the returned value when Math functions fail (Math.sqrt(-1)) or when a function trying to parse a number fails (parseInt("blabla")).
