What are the events of timer in javascript

JavaScript is a programming language widely used on the Internet. It has powerful functions and flexible application scope. In JavaScript, the timer is an important function that allows developers to control the execution time of the program, thereby achieving more accurate and efficient programming. In this article, I will introduce the event types of timers in JavaScript.

There are three main types of timer events in JavaScript: setTimeout, setInterval and clearInterval.

1. setTimeout event

The setTimeout event executes the specified function after a certain period of time. This function has two parameters, the function to be executed and the time to wait (in milliseconds). When the specified time has elapsed, the executed function will be called.

For example, the following code will pop up a prompt box after 5000 milliseconds (i.e. 5 seconds):

setTimeout(function(){
    alert("5秒后弹出提示框");
}, 5000);

2. setInterval event

The setInterval event is Execute the specified function repeatedly within a certain time interval. This function has two parameters, the function to be executed and the time to wait (in milliseconds). Every specified time, the executed function will be called.

For example, the following code will output the current time to the console every 1000 milliseconds (i.e. 1 second):

setInterval(function(){
    console.log(new Date());
}, 1000);

3. clearInterval event

The clearInterval event is used to stop repeated execution started by the setInterval event. It receives one parameter, the interval ID at which execution needs to be stopped. Therefore, when you need to stop the setInterval event, you can use this function.

For example, the following code will stop executing the setInterval event after 5 seconds:

var intervalId = setInterval(function(){
    console.log(new Date());
}, 1000);

setTimeout(function(){
    clearInterval(intervalId);
}, 5000);

In JavaScript, timer events are used very widely. By properly using setTimeout, setInterval and clearInterval events, developers can achieve various interesting functions and effects. However, in actual development, it should be noted that there are still some risks and defects in the use of timer events, such as performance degradation and excessive resource usage. Therefore, when using timer events, trade-offs and optimizations need to be made based on the actual situation to ensure the efficiency and stability of the program.

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