TypeScript 相对于 JavaScript 的优势是什么

    // TypeScript中的基本类型声明
    let age: number = 25;
    let name: string = 'Alice';
    let isStudent: boolean = true;
    
    // 尝试赋值错误类型的数据给age，会导致编译错误
    // age = 'twenty-five'; // 报错：Type 'string' is not assignable to type 'number'.
    
    
    typescript
    
    

    function greet(name: string): string {
    return `Hello, ${name}!`;
    }
    
    // 调用函数时传入错误类型的参数，会导致编译错误
    // greet(123); // 报错：Argument of type 'number' is not assignable to parameter of type 'string'.
    
    
    typescript
    
    

    let count = 10; // TypeScript自动推断count为number类型
    let message = 'Hello World'; // TypeScript自动推断message为string类型
    
    // 类型推断同样适用于函数返回值
    function add(a: number, b: number) {
    return a + b; // TypeScript自动推断返回值为number类型
    }
    
    
    typescript
    
    

    // 定义一个接口
    interface User {
    id: number;
    name: string;
    email?: string; // 可选属性
    }
    
    // 使用接口定义对象
    const user: User = {
    id: 1,
    name: 'Alice',
    email: 'alice@example.com'
    };
    
    // 定义一个枚举
    enum Role {
    ADMIN = 'admin',
    USER = 'user'
    }
    
    // 使用枚举
    const role: Role = Role.ADMIN;
    console.log(role); // 输出: admin
    
    
    typescript
    
    
![](https://ad.itadn.com/c/weblog/blog-img/images/2025-07-12/Uc5Phslw7uSL1GHAIqDirfMgykQW.png)

    // 定义一个类
    class Person {
    constructor(public name: string, public age: number) {}
    
    getDetails(): string {
        return `${this.name} is ${this.age} years old.`;
    }
    }
    
    // 创建一个Person实例
    const person = new Person('Bob', 30);
    
    // 在编辑器中输入person.，会显示可用的方法和属性
    console.log(person.getDetails()); // 输出: Bob is 30 years old.
    
    
    typescript
    
    
![](https://ad.itadn.com/c/weblog/blog-img/images/2025-07-12/C3xgWOQ0rNdTFB14kZ8D9Uo2wVsK.png)

    // 定义一个模块文件 math.ts
    export function add(a: number, b: number): number {
    return a + b;
    }
    
    export function subtract(a: number, b: number): number {
    return a - b;
    }
    
    // 在另一个文件中导入模块
    import { add, subtract } from './math';
    
    console.log(add(10, 5)); // 输出: 15
    console.log(subtract(10, 5)); // 输出: 5
    
    
    typescript
    
    
![](https://ad.itadn.com/c/weblog/blog-img/images/2025-07-12/npwx31bEMl9TsISPoJtkdymi0KOA.png)

    function getLength(input: string | number[]): number {
    if ((input as string).length) {
        return (input as string).length;
    } else {
        return input.length;
    }
    }
    
    console.log(getLength('hello')); // 输出: 5
    console.log(getLength([1, 2, 3])); // 输出: 3
    
    
    typescript
    
    
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    function isString(value: any): value is string {
    return typeof value === 'string';
    }
    
    function processValue(value: string | number) {
    if (isString(value)) {
        console.log(value.toUpperCase());
    } else {
        console.log(value.toFixed(2));
    }
    }
    
    processValue('hello'); // 输出: HELLO
    processValue(3.14159); // 输出: 3.14
    
    
    typescript
    
    
![](https://ad.itadn.com/c/weblog/blog-img/images/2025-07-12/1ehr90lPy8NAcTUDHanQ4gp3YBs5.png)

    type Coordinate = { x: number; y: number };
    
    function move(point: Coordinate, dx: number, dy: number): Coordinate {
    return { x: point.x + dx, y: point.y + dy };
    }
    
    const origin: Coordinate = { x: 0, y: 0 };
    const newPoint = move(origin, 1, 2);
    console.log(newPoint); // 输出: { x: 1, y: 2 }
    
    
    typescript
    
    

    function identity<T>(arg: T): T {
    return arg;
    }
    
    console.log(identity<string>('hello')); // 输出: hello
    console.log(identity<number>(42)); // 输出: 42
    
    
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    class Box<T> {
    private data: T;
    
    constructor(data: T) {
        this.data = data;
    }
    
    getData(): T {
        return this.data;
    }
    }
    
    const box = new Box<string>('hello');
    console.log(box.getData()); // 输出: hello
    
    
    typescript
    
    
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