函数定义

• 函数声明法

function add(n1: number, n2: number): number {return n1 + n2;
}；console.log(add(1, 2)); //3

• 函数表达式法

 var add = function (n1: number, n2: number): number {return n1 + n2;
};console.log(add(1, 2)); //3

类

class Greeter {greeting: string;constructor(message: string) {this.greeting = message;}greet() {return "Hello, " + this.greeting;}
}let greeter = new Greeter("world");

类带set/get方法

let passcode = "secret passcode";class Employee {private _fullName: string;get fullName(): string {return this._fullName;}set fullName(newName: string) {if (passcode && passcode == "secret passcode") {this._fullName = newName;}else {console.log("Error: Unauthorized update of employee!");}}
}let employee = new Employee();
employee.fullName = "Bob Smith";
if (employee.fullName) {alert(employee.fullName);
}
//我们可以修改一下密码，来验证一下存取器是否是工作的。当密码不对时，会提示我们没有权限去修改员工。

为函数定义类型

function add(x: number, y: number): number {return x + y;
}let myAdd = function(x: number, y: number): number { return x + y; };

?表示可选参数