What are the principles and mechanisms of asynchronous operations? How is it different from multithreading?

Asynchronous operation principle: Asynchronous operation technology allows the program to perform tasks without blocking the main thread, and notifies the main thread when the task is completed through the listener mechanism. The program creates listeners and associates them with tasks. The task is executed in the background and the main thread continues to run. When the task is completed, it calls the callback function in the listener to notify the main thread that the task is completed. Differences from multi-threading: Unlike multi-threading, asynchronous operations use a single thread to avoid concurrency issues and are more responsive, efficient, and easier to use.

The principle and mechanism of asynchronous operation:

Asynchronous operation is a technology that allows a program to perform tasks without blocking the main thread, thereby improving the response of the program sex and efficiency. It is implemented through a listener mechanism, which notifies the main thread when the task is completed.

Principle of asynchronous operation:

When an asynchronous operation is started, the program creates a listener and then associates the listener with the task. Program execution continues while tasks are executed in the background. Once the task is completed, the task calls a callback function in the listener. The callback function notifies the main thread that the task is completed, and the main thread can continue to process the results of the task.

How is it different from multithreading?

Multi-threading is another concurrent programming technique that achieves concurrency by creating multiple threads. Each thread has its own independent execution context, which contains its own stack and registers. While multithreading can improve a program's throughput, it can also lead to concurrency issues such as race conditions and deadlocks.

Asynchronous operations have the following advantages over multithreading:

• Responsiveness: Asynchronous operations allow programs to respond to user input and events without waiting for background tasks Finish.
• Efficiency: Asynchronous operations can process multiple tasks simultaneously in a single thread, thereby improving the overall efficiency of the program.
• Easy to use: The interface for asynchronous operations is generally simpler and easier to use because it does not require managing the life cycle of the thread.

Practical case:

The following is an example of using JavaScript to perform asynchronous operations:

// 创建一个异步函数
const asyncFunction = () => {
  // 模拟一个后台任务
  setTimeout(() => {
    console.log("任务完成！");
  }, 1000);
};

// 创建一个监听器
const listener = () => {
  console.log("任务完成的回调！");
};

// 启动异步函数并关联监听器
asyncFunction().then(listener);

// 主线程继续执行
console.log("程序还在继续运行！");

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