using typeof variable to determine js data type
using data type object for null value
Introduction with try and catch
introduction with undefined data type
global scope variables are stored first in js
introduction to window object
In Global scope this will be treated as window object
using self we can access windows object in global scope
all variables are in window object
using in operator to check whether the variable is in window object
'+' is an overloaded operator which will be used as arithmatic and string operator...
if we multiply a number with a string output will be NaN means not as number and NaN data type is number
isNaN function shows whether the value is NaN then true else false
Number function which type cast to number if the string is like number '123'
parseInt fucntion which type cast to Int when number like string  and number first string later string
undefined,number 0, null, emptystring will treated as false
Declaration of function and calling it
Introducing argument built in array
function can have two name funciton can be stored in a variable and to execute it we just need to use paranthesis
arguments array elements are initially undefined