理解装饰器模式

代码示例

1function decorate(originalFn) {
2  return function wrapped(...args) {
3    // 执行前的操作
4    const result = originalFn(...args);
5    // 执行后的操作
6    return result;
7  };
8}

Node.js

1// 模拟异步服务方法
2function fetchUserData(userId) {
3  return new Promise((resolve) => {
4    setTimeout(() => {
5      resolve({ id: userId, name: 'Alice' });
6    }, 100);
7  });
8}
9
10// 装饰器：测量执行时间
11function withTiming(fn) {
12  return async function (...args) {
13    const start = Date.now();
14    const result = await fn(...args);
15    const duration = Date.now() - start;
16    console.log(`[TIMER] ${fn.name} 花费了 ${duration}ms`);
17    return result;
18  };
19}
20
21// 应用装饰器
22const decoratedFetch = withTiming(fetchUserData);
23
24// 运行
25decoratedFetch(42);

TypeScript

1// 模拟异步服务方法
2function fetchUserData(userId: number): Promise<{ id: number; name: string }> {
3  return new Promise((resolve) => {
4    setTimeout(() => {
5      resolve({ id: userId, name: 'Alice' });
6    }, 100);
7  });
8}
9
10// 装饰器：测量执行时间
11function withTiming<T extends (...args: any[]) => Promise<any>>(fn: T): T {
12  return (async function (...args: any[]) {
13    const start = Date.now();
14    const result = await fn(...args);
15    const duration = Date.now() - start;
16    console.log(`[TIMER] ${fn.name || "Function"} 花费了 ${duration}ms`);
17    return result;
18  }) as T;
19}
20
21// 应用装饰器
22const decoratedFetch = withTiming(fetchUserData);
23
24// 运行
25decoratedFetch(42);