Javascript complete type list clarification?

Question

Dmitry Baranovskiy's blog (creator of Raphael) says that there are only 6 types in Javascript:

Object, Number, String, Boolean, Null, and Undefined.

Each can easily be checked via (for example):

Object.prototype.toString.apply(undefined) //"[object Undefined]"

But what about:

Object.prototype.toString.apply(new Date()) //"[object Date]"

Object.prototype.toString.apply(/a/)//"[object RegExp]"

...and Array, Functions also...

Are they different? Why are they not mentioned?

PS:

Is it related to the less-specific check like:

>>typeof [] //"object" ?

First ones are primitives. The ones you mention are native objects: en.wikipedia.org/wiki/JavaScript_syntax#Native_objects They are all of type "Object" — mishik
– mishik, Commented Jun 7, 2013 at 8:54
@mishik so how many types are? 6? ( each of testing starts with "object"] — Royi Namir
– Royi Namir, Commented Jun 7, 2013 at 8:57
Have a look here: es5.github.io/#x8-toc. There are only 6 data types you can interact with. "An ECMAScript language type corresponds to values that are directly manipulated by an ECMAScript programmer using the ECMAScript language. The ECMAScript language types are Undefined, Null, Boolean, String, Number, and Object." Functions, arrays and regular expressions are all objects. — Felix Kling
– Felix Kling, Commented Jun 7, 2013 at 9:01
@FelixKling thanks. please consider convert this to an answer. (Q :are you saying that this method [Object.prototype.toString.apply] is not the right method for type checking ?) — Royi Namir
– Royi Namir, Commented Jun 7, 2013 at 9:10
@RoyiNamir Is your question answered for now? Then mark it as it is! :) — yckart
– yckart, Commented Jun 7, 2013 at 9:48

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

According to the ECMAScript Language Specification, 5.1 Edition, §8:

An ECMAScript language type corresponds to values that are directly manipulated by an ECMAScript programmer using the ECMAScript language. The ECMAScript language types are Undefined, Null, Boolean, String, Number, and Object.

From this definition it seems that functions, arrays and regular expressions are of the Object type.

This might seem strange for functions, since you can do something with them you can't do with other objects: You can call them. However, this characteristic is simply an internal property which not all objects have (also in §8):

Table 9 — Internal Properties Only Defined for Some Objects

[[Call]] Executes code associated with the object. Invoked via a function call expression.

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Jun 7, 2013 at 10:31

Felix Kling

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Comments

yckart · Accepted Answer · 2013-06-07 08:54:17Z

0

Node, Element and HTMLElement are not types, just like Array, Date and RegExp they are just objects.

http://blogs.adobe.com/webplatform/2012/08/27/javascript-types/#comment-6038

answered Jun 7, 2013 at 8:54

yckart

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