函数的默认参数，可选参数，剩余参数

    //默认参数
    console.log('---默认参数---');
    function demo1(name:string = "默认参数"): void {
        console.log(name);
    };
    demo1();//return 默认参数
    demo1("传入参数");//return 传入参数
    // 可选参数
    console.log('---可选参数---');
    function demo2(name:string, age?: number): void {
        if (age !== undefined)
            return console.log(name + ',' + age);
        console.log(name);
    };
    demo2("传入参数1");//renturn 传入参数1
    demo2("传入参数2", 18);//renturn 传入参数2,18
    // 剩余参数
    console.log('---剩余参数---');
    function demo3(name:string, ...items:Array<any>):void {//items 声明类型时，必须时数组
        console.log('name:'+name);
        items.forEach(item => {
            console.log(item + ':' + name);
        });
    }
    demo3("剩余0");//return name:剩余0
    demo3("剩余1",1);//return name:剩余1 1:剩余1
    demo3("剩余3",1,2,3);//return name:剩余3 1:剩余3 2:剩余3 3:剩余3
    // 组合起来
    console.log('---组合起来---');
    function demo4(name?:string,...items:Array<any>):void{
        console.log('name:'+name);
        items.forEach(item=>{
            console.log('items'+item);
        });
    }
    demo4();//return name:undefined
    demo4("demo4");//return name:demo4
    demo4("items",1,2);//return name:items items1 items2