let a: boolean = true;

let a: number = 5;

let a: string = 'Hello';

//方法1
let a: [number] = [1, 2, 3];
//方法2
let a: Array<number> = [1, 2, 3];
//只读数组,数组的值不可以改变
let a: ReadonlyArray<number> = [1, 2, 3];

let a: [string, number] = ['11', 5];

enum Color = [Red=1, Blue, Green=9];
let a: Color = Color.Blue; //输出2
let a: string = Color[9]; //Green,索引从1开始

let a:any = 10;
a = 'Hello';

//void只能为它赋予undefined和null
let a: void = undefined;

let a: undefined = undefined;
let a: null = null;

let a: any = 'Hello';
let len: number = (<string>a).length;
//等价于上面
let len: number = (a as string).length;

let obj = {
  a: 11,
  b: 'Jone',
  c: 33
};
let {a: a1, b: b1} = obj;
console.log(a1+'--'+b1); //11--Jone

function test(value: {a: string, b?: number}){
  let {a, b=55} = value;
  console.log(a+'--'+b);
}
test({a: 'Hello'}); //b可以省略不写，默认为55