data type javascript

                                    //String Data Type
var strSingle = 'John'; //String with single quotes
var strDouble = "Bob"; //String with double quotes

//Number Data Type
var num = 25; //Integer
var flo = 80.5; //Floating-point number
var exp = 4.25e+6; //Exponential notation, this equates to 4250000

//Boolean Data Type
var isReading = true; //Yes, I'm reading
var isSleeping = false; //No, I'm not sleeping

//Undefined Data Type
var undef; //If a value is never assigned, any output will be 'undefined'

//Null Data Type
var noValue = null; //Null meaning that it is has no value, not the same as 0 or ""

//Object Data Type
var emptyObject = {};
var person = {"name": "Clark", "surname": "Kent", "age": "36"}; //The quotes around the propety name can be omitted if the property name is a valid JS name
var car = { //Same as person but easier to read
	model: "BMW X3", //Example with quotes around property name ommitted
	color: "white",
	doors: 5
}

//Array Data Type
var emptyArray = []; //An array can be of any data types (string, number, boolean, etc.)
var array = ["One", "Two"] //String array, note the index of the first element is 0

//Function Data Type
var func = function() { //Calling the function: func();
  alert("Code excuted"); //Outputs: Code executed
}

var funcVar = function(amount) { //Calling the function: funcVar(6); 
  alert("Code excuted " + amount + " times"); //Outputs: Code executed 6 times (if input was 6)
}

//Typeof Operator
typeof variable; //Returns the data type of the variable

                                    //There are 7 data types in JS 
//They're split in two categories - (Primitives and Complex Types)

//Primives
string, number, boolean, null, undefined

//Complex types
Object, Function

                                    var age = 18;                           // number 
var name = "Jane";                      // string
var name = {first:"Jane", last:"Doe"};  // object
var truth = false;                      // boolean
var sheets = ["HTML","CSS","JS"];       // array
var a; typeof a;                        // undefined
var a = null;                           // value null

                                    dataTypes = {
    Numbers = 1,2,3, 100, 3.14
    Strings = 'Hello, World' "[email protected]
    Boolean = true / false
    Null = 'Explicitly set a variable with no Value'
    Undefined = 'For variable that have not yet been defined'
    Object = 'Complex data structures - Arrays, Dates, Literals etc'
    Symbol = 'Used with objects' // usually not needed
}

                                    /*JavaScript data types*/
//string
var string = 'ASCII text';
//int
var integer = 123456789;
//float
var float = 123.456;
//boolean, can be true or false
var t = true;
var f = false;
//undefined
var undef;//defaults to undefined
var undef = undefined;//not common, use null
//null
var nul = null;
//array
var arr = ['Hello','my','name','is','Dr.Hippo',123,null];
//object
var person = {'name':'John Smith','age':27};
//function
var fun = function(){
    return 42;
}