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TypeScript基础教程

TypeScript简介

TypeScript是微软开发的一种开源编程语言，它是JavaScript的超集，添加了可选的静态类型和基于类的面向对象编程。TypeScript在编译时提供类型检查，可以在开发阶段就发现潜在错误，提高代码质量和开发效率。

TypeScript的优势

• 静态类型检查：捕获开发阶段的错误
• 增强的IDE支持：提供代码补全和智能提示
• ES6+特性支持：支持最新的JavaScript特性
• 面向对象编程：提供类、接口、继承等OOP特性
• 大型项目可维护性：类型系统使大型项目更易于维护和重构

环境搭建

安装Node.js和npm

首先需要安装Node.js和npm，可以从Node.js官网下载安装包。

安装TypeScript

安装完Node.js后，使用npm全局安装TypeScript：

npm install -g typescript

验证安装成功：

tsc --version

创建第一个TypeScript文件

1. 创建一个名为hello.ts的文件：

function greet(name: string) {return `Hello, ${name}!`;
}console.log(greet("TypeScript"));

1. 编译TypeScript文件：

tsc hello.ts

这将生成hello.js文件。

1. 运行JavaScript文件：

node hello.js

基本类型

TypeScript支持多种数据类型：

布尔值

let isDone: boolean = false;

数字

let decimal: number = 6;
let hex: number = 0xf00d;
let binary: number = 0b1010;
let octal: number = 0o744;

字符串

let color: string = "blue";
let fullName: string = `Bob Bobbington`;
let sentence: string = `Hello, my name is ${fullName}`;

数组

let list: number[] = [1, 2, 3];
let list2: Array<number> = [1, 2, 3]; // 泛型数组类型

元组

let x: [string, number];
x = ["hello", 10]; // 正确
x = [10, "hello"]; // 错误

枚举

enum Color {Red, Green, Blue}
let c: Color = Color.Green;

Any

let notSure: any = 4;
notSure = "maybe a string";
notSure = false; // 也可以是布尔值

Void

function warnUser(): void {console.log("This is a warning message");
}

Null和Undefined

let u: undefined = undefined;
let n: null = null;

Never

function error(message: string): never {throw new Error(message);
}

Unknown

let value: unknown;
value = true; // OK
value = 42; // OK

变量声明

TypeScript支持JavaScript的var、let和const关键字，但推荐使用let和const。

let hello = "Hello!";
const PI = 3.14159;

类型断言

let someValue: any = "this is a string";
let strLength: number = (<string>someValue).length;
// 或
let strLength2: number = (someValue as string).length;

函数

函数类型

function add(x: number, y: number): number {return x + y;
}// 函数类型表达式
let myAdd: (x: number, y: number) => number = function(x, y) { return x + y; };

可选参数和默认参数

function buildName(firstName: string, lastName?: string): string {return lastName ? firstName + " " + lastName : firstName;
}function buildName2(firstName: string, lastName = "Smith"): string {return firstName + " " + lastName;
}

剩余参数

function buildName(firstName: string, ...restOfName: string[]): string {return firstName + " " + restOfName.join(" ");
}

接口

接口定义了对象的结构和约束。

interface Person {firstName: string;lastName: string;age?: number; // 可选属性readonly id: number; // 只读属性
}function greet(person: Person) {return `Hello, ${person.firstName} ${person.lastName}`;
}let user: Person = {firstName: "John",lastName: "Doe",id: 1
};

实现接口

interface ClockInterface {currentTime: Date;setTime(d: Date): void;
}class Clock implements ClockInterface {currentTime: Date = new Date();setTime(d: Date) {this.currentTime = d;}constructor(h: number, m: number) { }
}

类

TypeScript提供了基于类的面向对象编程支持。

class Animal {name: string;constructor(theName: string) {this.name = theName;}move(distanceInMeters: number = 0) {console.log(`${this.name} moved ${distanceInMeters}m.`);}
}class Dog extends Animal {constructor(name: string) {super(name);}bark() {console.log('Woof! Woof!');}move(distanceInMeters = 5) {console.log("Running...");super.move(distanceInMeters);}
}const dog = new Dog("Rex");
dog.bark();
dog.move(10);

访问修饰符

class Animal {private name: string;protected age: number;public color: string;constructor(name: string, age: number, color: string) {this.name = name;this.age = age;this.color = color;}
}

静态属性

class Grid {static origin = {x: 0, y: 0};calculateDistanceFromOrigin(point: {x: number; y: number;}) {let xDist = point.x - Grid.origin.x;let yDist = point.y - Grid.origin.y;return Math.sqrt(xDist * xDist + yDist * yDist);}
}

泛型

泛型允许创建可重用的组件，适用于多种类型而不是单一类型。

function identity<T>(arg: T): T {return arg;
}// 调用泛型函数
let output = identity<string>("myString");
// 或者使用类型推断
let output2 = identity("myString");

泛型接口

interface GenericIdentityFn<T> {(arg: T): T;
}let myIdentity: GenericIdentityFn<number> = identity;

泛型类

class GenericNumber<T> {zeroValue: T;add: (x: T, y: T) => T;
}let myGenericNumber = new GenericNumber<number>();
myGenericNumber.zeroValue = 0;
myGenericNumber.add = function(x, y) { return x + y; };

模块与命名空间

导出

// 文件: math.ts
export function add(x: number, y: number): number {return x + y;
}

导入

// 文件: main.ts
import { add } from "./math";console.log(add(1, 2));

命名空间

namespace Validation {export interface StringValidator {isAcceptable(s: string): boolean;}export class LettersOnlyValidator implements StringValidator {isAcceptable(s: string) {return /^[A-Za-z]+$/.test(s);}}
}let validator = new Validation.LettersOnlyValidator();

TypeScript配置

创建tsconfig.json文件配置TypeScript编译选项：

{"compilerOptions": {"target": "es5","module": "commonjs","strict": true,"esModuleInterop": true,"outDir": "dist"},"include": ["src/**/*"],"exclude": ["node_modules"]
}

实战示例

创建一个简单的待办事项应用

// 定义Todo接口
interface Todo {id: number;title: string;completed: boolean;
}// 创建TodoApp类
class TodoApp {private todos: Todo[] = [];private nextId: number = 1;addTodo(title: string): Todo {const todo: Todo = {id: this.nextId++,title,completed: false};this.todos.push(todo);return todo;}toggleTodo(id: number): Todo | undefined {const todo = this.getTodo(id);if (todo) {todo.completed = !todo.completed;return todo;}return undefined;}removeTodo(id: number): boolean {const initialLength = this.todos.length;this.todos = this.todos.filter(todo => todo.id !== id);return initialLength !== this.todos.length;}getTodo(id: number): Todo | undefined {return this.todos.find(todo => todo.id === id);}getAllTodos(): Todo[] {return this.todos;}
}// 使用TodoApp
const app = new TodoApp();
app.addTodo("学习TypeScript");
app.addTodo("创建项目");
const todo3 = app.addTodo("发布应用");app.toggleTodo(2); // 将"创建项目"标记为已完成console.log(app.getAllTodos());

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这个教程涵盖了TypeScript的基础知识。要深入学习TypeScript，建议参考TypeScript官方文档和其他进阶资源。