let 定义变量 

let num1: number = 10;

let str: string = 'xiaoming';

let nums: number[] = [1,2,3];

let nums2:Array<number> = [4,5,6];

| 联合类型 || 逻辑或 `模板字符串符号

表达式定义函数

let add2:(x: number ,y： number) => number = (x,y) =>{

return x + y

}

function add(x: number,y: number):number{

return x+y;

}

定义数组：

let list:Array<string|number> = [1,"xiaoming",2,"xiaohong",3,"xiaozhu"]