How many data types are there in JS, and what are they?

Question

I started reading a book, Javascript for Kids. In it the author states that there are three data types:

• numbers
• strings
• booleans

Answer 1

Things aren't actually as straightforward as they described in answers above... they usually aren't in javascriptland ;)

typeof is the 'official' function that one uses to get the type in javascript, however in certain cases it might yield some unexpected results ...

1. Strings

typeof "String" or
typeof Date(2011,01,01)

"string"

2. Numbers

typeof 42 or
typeof NaN, lol

"number"

3. Bool

typeof true (valid values true and false)

"boolean"

4. Object

typeof {} or
typeof [] or
typeof null or
typeof /aaa/ or
typeof Error()

"object"

5. Function

typeof function(){}

"function"

6. Undefined

var var1; typeof var1

"undefined"

Alternative is to use ({}).toString() which will get you somewhat more accurate answer most of the time...