TypeScript的函数

// 类型别名
type ISum = (x: number, y: number) => number
// 应用如下：
let sum: ISum = (a, b) => a + b
console.log(sum(3, 2));

//函数重载
function fn(name: string): string;
function fn(age: number): number;
function fn(nameorage: any): any {
    if (typeof nameorage == "string") {
        return "姓名:" + nameorage;
    } else if (typeof nameorage == "number") {
        return "年龄:" + nameorage
    }
}
// 姓名:张培跃
console.log(fn("张2"));
// 年龄:18
console.log(fn(666));

//======函数重载====反转数字或字符串
function reverse(num: number): number;
function reverse(str: string): string;
function reverse(val: any): any {
  if (typeof val === 'number') {
    return Number(val.toString().split('').reverse().join(''))
  } else if (typeof val === 'string') {
    return val.split('').reverse().join('')
  }
  return false
}

console.log(reverse(123456))  // 654321
console.log(reverse('sina'))  // 'anis'

//函数的 剩余参数
function sum2(num1: number, ...rest: number[]): number {
    interface ITotal {
      (pre: number, cur: number): number;
    }
    const handle: ITotal = (pre, cur) => pre + cur
    return rest.reduce(handle, num1)
  }
  
console.log(sum2(1, 2, 3, 4, 5, 6, 7)); // 28

//====缺省的第1个参数，this 指针
function fun3(this:any, para1:number,para2:number)
{
    console.log(para1);
    console.log(para2);
}

fun3(1,2);//1,2