类型注解

function greeter(person: string) {
    return "Hello, " + person;
}

接口

interface Person {
    firstName: string;
    lastName: string;
}

function greeter(person: Person) {
    return "Hello, " + person.firstName + " " + person.lastName;
}

类

class Student {
    fullName: string;
    constructor(public firstName, public middleInitial, public lastName) {
        this.fullName = firstName + " " + middleInitial + " " + lastName;
    }
}

interface Person {
    firstName: string;
    lastName: string;
}

function greeter(person : Person) {
    return "Hello, " + person.firstName + " " + person.lastName;
}

let user = new Student("Jane", "M.", "User");

document.body.innerHTML = greeter(user);

注意

这里的类和 ES6 的类有些许差别

• 支持在 constructor 外定义属性
• 在 constructor 定义的 public 属性会自动成为该类的公有属性（这里还可以为 private、protected）

所以这里的 Student 在实例化成 user 后拥有 4 个属性如下

user; // {fulName: "Jane M. User", firstName: "Jane", middleInitial: "M.", lastName: "User"}