What is JavaScript?
Javascript is a client-side as well as a server-side scripting language that can be inserted into HTML pages and is understood by web browsers. JavaScript is also an Object-based Programming language

Enumerate the differences between Java and JavaScript?
Java is a complete programming language. In contrast, JavaScript is a coded program that can be introduced to HTML pages. These two languages are not at all inter-dependent and are designed for different intent. Java is an object-oriented programming (OOPS) or structured programming languages like C++ or C whereas JavaScript is a client-side scripting language.

What are JavaScript Data Types?
Following are the JavaScript Data types:
Number, String, Boolean, Object, Undefined

What is the use of isNaN function?
isNan function returns true if the argument is not a number otherwise it is false.

isNaN(123) //false
isNaN(-1.23) //false
isNaN(5-2) //false
isNaN(0) //false
isNaN('123') //false
isNaN('Hello') //true
isNaN('2005/12/12') //true
isNaN('') //false
isNaN(true) //false
isNaN(undefined) //true
isNaN('NaN') //true
isNaN(NaN) //true
isNaN(0 / 0) //true

Difference between event.stopPropagation and event.preventDefault
stopPropagation prevents further propagation of the current event in the capturing and bubbling phases.
preventDefault prevents the default action the browser makes on that event.