How to write JavaScript after a few seconds

JavaScript is a scripting language widely used in web applications. Through JavaScript, developers can add dynamic effects, interactivity and web page behaviors to web pages. When writing JavaScript programs, we often need to execute certain code after a certain period of time, such as executing a function or jumping to another page after a few seconds. So, how does JavaScript implement this function?

1. Use setTimeout()

The setTimeout() function is a method in JavaScript used to delay the execution of a certain function. This function accepts two parameters: one is the function to be executed, and the other is the number of milliseconds to delay. The code example is as follows:

function func() {
  console.log("执行函数");
}

setTimeout(func, 3000); // 延迟3秒执行

Through the above code, we define a function func(), and then set the function to execute after 3 seconds. After 3 seconds, the console will output the message "Execute function".

2. Use Promise

Promise is a solution for asynchronous programming. It can wrap asynchronous operations into an object, making it easier to process. Using Promise, we can implement the function of performing an operation after a certain period of time. The code example is as follows:

function func() {
  console.log("执行函数");
}

function delay(time) {
  return new Promise((resolve, reject) => {
    setTimeout(resolve, time);
  });
}

delay(3000).then(func); // 延迟3秒执行

In the above code, we first define a function func() to represent the operation that needs to be performed after a certain time. Then, we defined a delay() function, which accepts a time parameter and returns a Promise object. In the Promise object, we use the setTimeout() function to implement delayed operations. Finally, when calling the delay() function, we use the then() method to specify the function to be executed after the delay time expires.

3. Use async/await

async/await is a new feature introduced in ES2017. It is a further encapsulation and simplification of Promise. With the help of async/await, we can make the code more concise and easy to understand to implement the function of performing an operation after a certain time. The code example is as follows:

function delay(time) {
  return new Promise((resolve, reject) => {
    setTimeout(resolve, time);
  });
}

async function func() {
  await delay(3000);
  console.log("执行函数");
}

func(); // 延迟3秒执行

In the above code, we first define a delay() function, which returns a Promise object for implementing delayed operations. Then, we defined an async function func(), in which we use the await keyword to wait for the delay time to expire before performing the operation. Finally, when calling the func() function, we can implement the function of performing an operation after a certain time.

Summary

This article introduces how JavaScript can implement the function of performing an operation after a certain period of time. By using the setTimeout() function, Promise and async/await, we can flexibly implement this function and make the code more concise and easy to understand. In actual development, we can choose the appropriate implementation method according to specific needs to better deal with the problem of delayed execution operations.

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