JavaScript Data Types

There are seven data types in ECMAScript . Six of them are simple data types , you can call them primitive types : Undefined , Null , Boolean , Number , String and Function . One is complex data type : Object . Maybe you would ask what about Array , custom objects and others . Well , good question . Because I am talking about data types , more specificly , data types in ECMAScript . I will explain later .

    As you know I split data types into two part . So I will explain them with two part . 

    First ,  primitive types . These are the simple data types . Like data types in C++ . These are basic . You can test any statements with typeof operator , and then it will show you one of them , and just seven of them . 

    Undefined : Just one value , undefined . 1. When a variable is declared using var but not initialized , it is assigned the value of undefined . 2. When you use a variable which is not declared , it is assigned the value of undefined . 

    Null : Just Like Undefined , one value , null . It is a value of an empty object pointer . So this why you typeof a variable which the value is null will return "object" . Like : 

var nullType = null;
console.log(nullType); // object 

    Boolean : Like C++ , have two values : true and false . And one thing I have to mention is Boolean() . It is a function that you can reverse some variables not type of boolean to boolean . Here are the rules : 

Boolean	true	false
String	Any not empty string	""
Number	Not Zero	0 & NaN
Object	Any object	null
Undefined	N/A	undefined

    Number : Included Int , Float and NaN . I will explain the NaN , AKA , not a number . It is not equal to anything , included itself . 

    String : You can define a string like : | var string = "" ; | . So simple . But here is one function I want to talk about : toString() . It is a function of String . Means you can call it with any variable , like : | myVariable.toString(); | . Then it will return a string of the variable by some rules . You can just think it in this way : return the string that the value of it . Like boolean : a true variable return "true" . 

    Function : You know , just simple , it will return function with using the typeof operator when it is a function . 

    OK , I explained six simple data types . Next , I will explain the last one , Object . 

    Object : It includes Object , Array , custom object ... But I just show you the code . 

var undefinedType = undefined;

var nullType = null;

var booleanType = true;

var numberType = 2;

var stringType = "data type";

var functionType = function() {
	alert("Data Type");
};

var objectType = new Object();

var arrayType = new Array();

var customObjectType = {
	name: "Root"
};

console.log(typeof undefinedType); // undefined

console.log(typeof nullType); // object

console.log(typeof booleanType); // boolean

console.log(typeof numberType); // number 

console.log(typeof stringType); // string

console.log(typeof functionType); // function

console.log(typeof objectType); // object

console.log(typeof arrayType); // object

console.log(typeof customObjectType); // object

    So I hope this will help you . Good luck .