nodejs sleep method

Node.js is an event-driven asynchronous server-side JavaScript runtime environment. It is lightweight, power efficient and scalable. However, due to the asynchronous execution model of Node.js, there are some cases where wait/delay operations similar to synchronous operations need to be manually implemented. Sleep operations are often used to simulate long-running operations or in certain tasks that need to be executed after a period of time. This article will introduce how to implement sleep operations in Node.js.

Method 1: Use the setTimeout function

The setTimeout method is a built-in function of Node.js, which can be used to trigger a callback function after a specified number of milliseconds. We can use this feature to simulate sleep operations.

The following is an example:

function sleep(ms) {
    return new Promise(resolve => setTimeout(resolve, ms));
}

async function main() {
    console.log('start');
    await sleep(2000); // 睡眠2秒
    console.log('end');
}

main();

In the above code, we define an asynchronous function sleep, which will return a Promise object and call the resolve method after the specified number of milliseconds. The function main calls the sleep function and waits for 2 seconds before outputting a line of log. Through async/await syntax, we can implement sleep operations very conveniently.

Method 2: Use a custom Promise object

We can also implement a Promise object ourselves to implement sleep operations. This method is more flexible and you can customize the execution method of Promise objects according to your own needs.

The following is an example:

function sleep(ms) {
    return new Promise(resolve => {
        let startTime = new Date().getTime();
        while (new Date().getTime() < startTime + ms);
        resolve();
    });
}

async function main() {
    console.log('start');
    await sleep(2000); // 睡眠2秒
    console.log('end');
}

main();

In this example, we define a function sleep that will execute a loop (for simulation timing) within the specified number of milliseconds. When the loop ends, we call the resolve method to end the execution of the Promise. The function main calls the sleep function and waits for 2 seconds before outputting a line of log.

It should be noted that this method will also occupy CPU resources while implementing sleep operations. It is not recommended to be used in a production environment and is only used under special circumstances when long-running operations need to be simulated.

Conclusion

No matter which method is used, implementing sleep operations is simple. Although the asynchronous execution model of Node.js is good at handling high-concurrency requests, we also have a variety of methods to implement some operations that require waiting/delay. It is necessary to choose the appropriate implementation method according to actual needs.

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