Lecture 1: Javascript, Data Types, Variables

- A scripting language interpreted in Browser (Client Side). Source code is delivered to client side - Also compiled in server and only result is delivered to client. Eg. Node.js - Also used in Game Engines (Unity), Mobile Applications, Query languages (Couch DB), Mongo DB

Exercises - Running JavaScript in Console - Running JavaScript in Browser Web Page

Data Types

- String

var greet = 'Hello, How are you?';
var review = "It's good";
var sentence = 'He said,"I\'m coming"';

-Number (64 bits)

var x = 50.00;     // Written with decimals
var y = 50;        // Written without decimals
var y = 123e4;      // 1230000
var z = 123e-4;     // 0.0123

Special Numbers Infinity, -Infinity, NaN (eg: Infinity-Infinity)

-Boolean

var x = true;
var y = false;
console.log(3>2);  //true
console.log("aa"<"bb"); //true
isNaN("Hello"); //true

-undefined & null

var x;      // x is undefined
var a = null;   // must be explicitly defined as null

Data Type Behaviour

-Automatic Data Conversion

var x = 1 + "Kathmandu";
var x = 1 + 2 + "Patan";
var x = "Kathmandu" + 2 + 1;
console.log("10" - 2);
console.log("ten"*10);
console.log(false==0);
null==undefined; //true
null==0; //false

- type of Operator

var x;               // x is undefined
console.log(typeof(x));

var x = 5;           // x is a Number
var x = "John";      // x is a String

Variables

-Variables hold values.

var num; num = 3;
var name = "Modi", age = 60;
var result = num *3; $y = "me";

-Variable Names -Begin with letters, $ or _ -Only contain letters, numbers, $ and _ -Case sensitive -Dont use Keywords

break case catch class const continue debugger default delete do else 
enum export extends false finally for function if implements import in 
instanceof interface let new null package private protected public return 
static super switch this throw true try typeof var void while with yield

Exercise

-Ex 1 Take first name, last name and birth year from a user and calculate his age. Show an output that says " Firstname LastName, you are NN years old". Use getFullYear() method of Date object to get current year. Do this task in the console and in the browser as well. For help - http://www.w3schools.com/js/js_dates.asp…

- Ex 2 Modify solution of Ex 1 to ask birthmonth and birthdate along with birth year of the user. Use other Methods of Date object to calculate exact age (years, month and days) of the user. Seek help from http://www.w3schools.com/js/js_date_meth…