why isn't "function" considered a datatype in javascript?

Question

The datatypes listed in MSDN for javascript are Number, String, Boolean, Object, Array, Null, Undefined. However, when you do typeof function, its type is function.

Why is this the case, and what's the definition of datatype?

That list is essentially meaningless. Arrays are regular objects. — SLaks
– SLaks, Commented Oct 13, 2014 at 16:22
typeof is special and doesn't actually return the type of the value (according to the spec). It's just a lookup table: ecma-international.org/ecma-262/5.1/#sec-11.4.3 — Felix Kling
– Felix Kling, Commented Oct 13, 2014 at 16:46

Prabhu Murthy · Accepted Answer · 2014-10-17 05:29:02Z

3

Functions are just Objects in JavaScript. But the difference lies in an internal property called [[Call]] that differentiates them from normal Objects. When typeof is used against an Object, and if it finds the [[Call]] property, then it returns the String "function".

This behavior can be found in the ECMA Specification for typeof.

edited Oct 17, 2014 at 5:29

answered Oct 13, 2014 at 16:24

Prabhu Murthy

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3 Comments

Luizgrs Over a year ago

Are you saying typeof { Call: function(){ } } should return function?

Ian Over a year ago

@Luizgrs ecma-international.org/ecma-262/5.1/#sec-13.2.1 - [[Call]] is an internal property

Luizgrs Over a year ago

with the specs it's now clear, I thought that brackets meant something but I couldn't understand, now it's fine..

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