What are the data types returned by typeof

There are 6 data types returned by typeof, namely: 1. object, object type; 2. undefined, undefined type; 3. string, string type; 4. number, numeric type; 5. boolean, Boolean type; 6. function, function type.

typeof returns a total of 6 data formats:

1, object      —Variables or values of object type, Or null (this is a problem left by JS history, treat null as the Object type)

2, UNDEFINED-Unfalted variables or values

3, String-String-string type variables Or value

4、number --Numeric type variable or value

5、boolean --Boolean type variable or value

6、function --Function type Variable or value

Example:

Undefined

var a1; typeof(a1);

Run result:

number

var num1=12; typeof(num1);

Run result:

string

var num2="12"; typeof(num2);

Run result:

boolean

var flag=true; typeof(flag);

Run result:

object

var str=new String(); typeof(str); var a=null; typeof(a);

Run result:

function

var fn = function(){}; typeof(fn); typeof(class c{});

Run result:

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