在所有异步操作完成时通知执行多个异步操作(Typescript)

在所有异步操作完成时通知执行多个异步操作是一种常见的编程需求，可以通过使用Promise、async/await和事件机制来实现。

使用Promise：
- 创建一个Promise数组，每个Promise代表一个异步操作。
- 使用Promise.all()方法将这些Promise组合成一个新的Promise。
- 当所有异步操作都完成时，新的Promise将被解析，并可以执行下一步操作。

示例代码：

const asyncOperation1 = (): Promise<string> => {

 return new Promise((resolve) => {

   setTimeout(() => {

     resolve("Async operation 1 completed");

   }, 1000);

});

};

const asyncOperation2 = (): Promise<string> => {

 return new Promise((resolve) => {

   setTimeout(() => {

     resolve("Async operation 2 completed");

   }, 2000);

});

};

const asyncOperation3 = (): Promise<string> => {

 return new Promise((resolve) => {

   setTimeout(() => {

     resolve("Async operation 3 completed");

   }, 1500);

});

};

const executeAsyncOperations = async (): Promise<void> => {

 const promises = [asyncOperation1(), asyncOperation2(), asyncOperation3()];

 await Promise.all(promises);

 console.log("All async operations completed");

 // 执行其他操作

};

executeAsyncOperations();

使用async/await：
- 将异步操作封装成一个异步函数，并使用async关键字修饰。
- 在函数内部使用await关键字等待异步操作完成。
- 调用这些异步函数时，使用await关键字等待它们的完成。

示例代码：

const asyncOperation1 = (): Promise<string> => {

 return new Promise((resolve) => {

   setTimeout(() => {

     resolve("Async operation 1 completed");

   }, 1000);

});

};

const asyncOperation2 = (): Promise<string> => {

 return new Promise((resolve) => {

   setTimeout(() => {

     resolve("Async operation 2 completed");

   }, 2000);

});

};

const asyncOperation3 = (): Promise<string> => {

 return new Promise((resolve) => {

   setTimeout(() => {

     resolve("Async operation 3 completed");

   }, 1500);

});

};

const executeAsyncOperations = async (): Promise<void> => {

 await asyncOperation1();

 await asyncOperation2();

 await asyncOperation3();

 console.log("All async operations completed");

 // 执行其他操作

};

executeAsyncOperations();

使用事件机制：
- 创建一个事件触发器，用于通知异步操作的完成。
- 在每个异步操作完成时，触发相应的事件。
- 创建一个监听器，监听所有异步操作完成的事件。
- 当所有异步操作都完成时，执行下一步操作。

示例代码：

import { EventEmitter } from "events";

const asyncOperation1 = (): Promise<string> => {

 return new Promise((resolve) => {

   setTimeout(() => {

     resolve("Async operation 1 completed");

   }, 1000);

});

};

const asyncOperation2 = (): Promise<string> => {

 return new Promise((resolve) => {

   setTimeout(() => {

     resolve("Async operation 2 completed");

   }, 2000);

});

};

const asyncOperation3 = (): Promise<string> => {

 return new Promise((resolve) => {

   setTimeout(() => {

     resolve("Async operation 3 completed");

   }, 1500);

});

};

const executeAsyncOperations = async (): Promise<void> => {

 const eventEmitter = new EventEmitter();

 const asyncOperationCompleted = (): void => {

   if (

     eventEmitter.listenerCount("asyncOperation1") === 0 &&

     eventEmitter.listenerCount("asyncOperation2") === 0 &&

     eventEmitter.listenerCount("asyncOperation3") === 0

) {

     console.log("All async operations completed");

     // 执行其他操作

};

 eventEmitter.on("asyncOperation1", asyncOperationCompleted);

 eventEmitter.on("asyncOperation2", asyncOperationCompleted);

 eventEmitter.on("asyncOperation3", asyncOperationCompleted);

 asyncOperation1().then((result) => {

   console.log(result);

   eventEmitter.emit("asyncOperation1");

});

 asyncOperation2().then((result) => {

   console.log(result);

   eventEmitter.emit("asyncOperation2");

});

 asyncOperation3().then((result) => {

   console.log(result);

   eventEmitter.emit("asyncOperation3");

});

};

executeAsyncOperations();

这种方法可以应用于各种场景，例如同时请求多个API并在所有请求完成后进行数据处理，或者在多个文件下载完成后进行文件合并等。腾讯云提供了一系列云计算产品，如云函数SCF、云数据库CDB、云存储COS等，可以根据具体需求选择适合的产品来实现异步操作的通知和处理。具体产品介绍和文档可以在腾讯云官网上找到。