Basics of Type Script

1. To define a Variable. 

　　There are two ways. Let and Var

Var a = 3;

Let b = 4; 

　　The difference between Let and Var 

2. Data type. 

//Boolean 

　　var bn: boolean = true　

var bn:boolean = true;
console.log(bn);

  // Number type

　　var num:Number = 111;

　　var num2:Number = 3.14;

//String 

　　var str:string = 'aaaa';

//Arrays

　　var arr:numer[] = [11,22,33,44];

　　var  arr: Array<number> = [11,22,33,44];

//Enum

　　enum color {red, green, yellow, blue};

　　color[0]  = red

　example 2

　　enum color1 { red = 1, green =3, yellow = 5, blue}

　 　　color1[3] =green 

　　　 color1[5] = yellow

　　　 color1[6] = blue

//Any

　　var tmp:any[] = ['aaa', 1111, 22, 3.4]  //this will not throw error

//Void

　　function NAME(): string {

   

　　return  "String";

}   //this function must return type String as defined. 

　　function NAME() : void {

　　}

3. Constant variable