TypeScript : The Superset of Javascript

1. Static Typed
2. File extension : .ts
3. .ts file is compiled to create .js file
4. Execution format ts : tsc <fileName.ts>
5. After .js file is created use command : node <fileName.js>
6. Semi-colon at the end is optional in TypeScript
7. Refer typescriptplay.ts and typescriptplay.js above.

main.ts : 
var message:string ='hello world';
console.log(message);

C:\nodejs-play\nodejs-play-1> tsc main.ts
C:\nodejs-play\nodejs-play-1> node main.js

Type Assertion. Kind of type casting in C++/JAVA

var str = '100';
var num:number = <number> <any> str;
console.log(num);

functions with Rest parameters

function addsum(...nums:number[]){
    var sum = 0;
    for (var i = 0; i < nums.length; i++) {
        sum+=nums[i];
    }
    console.log(sum);
}

addsum(1,2,3,4);

function overloading

function disp(s1:string):void; 
function disp(n1:number,s1:string):void; 
// '?' refers that argument is optional
function disp(x:any,y?:any):void { 
   console.log(x); 
   if(y!=undefined)
   console.log(y); 
} 
disp("abc");
disp(1,"xyz");

Tuples

Kind of an array but can contain values of different types

var myTuple = [10,'hello','world'];
console.log(myTuple[1]);

Union Type

Declaring a variable with multiple data types

var num2:number|string;
num2 = 1;
console.log(num2);
num2 = 'hello';
console.log(num2);
 //num2 = true; throws error because num2 is not of Boolean type

interface

interface IPerson { 
   firstName:string, 
   lastName:string, 
   sayHi: ()=>string 
} 

var customer:IPerson = { 
   firstName:"Quentin",
   lastName:"Tarantino", 
   sayHi: ():string =>{return "Hi there"} 
} 

console.log(customer.firstName) 
console.log(customer.lastName) 
console.log(customer.sayHi())  

class and objects

 class Animal{
    name:string;
    color : string;
    constructor(name:string,color:string){
        this.name = name;
        this.color = color;
    }
};

var obj = new Animal('Dog','White');
console.log('Animal name is : '+obj.name+'  , Animal color is : '+obj.color);

Access Specifiers

Similar to C++/JAVA

class Animall{
    name:string;
    private color : string;
    constructor(name:string,color:string){
        this.name = name;
        this.color = color;
    }
};

var objj = new Animall('Dog','White');
console.log('Animal name is : '+obj.name+'  , Animal color is : '+objj.color); //Error because field color is private

Changes to objects

var person = {
   firstName:"Tom", 
   lastName:"Hanks", 
   sayHello:function() {  }  //Type template 
} 
person.sayHello = function() {  
   console.log("hello "+person.firstName)
}  
person.sayHello();

Passing objects as parameters

interface IPoint { 
    x:number 
    y:number 
 } 
 function addPoints(p1:IPoint,p2:IPoint):IPoint { 
    var x = p1.x + p2.x 
    var y = p1.y + p2.y 
    return {x:x,y:y} 
 } 
 
 var newPoint = addPoints({x:3,y:4},{x:5,y:1});
 console.log(newPoint);