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This article mainly explains "what is the function of javascript timer". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the train of thought of Xiaobian to study and learn what function javascript timer has.

Javascript timer has two functions, namely: 1, setTimeout () function, used to execute some code after a specified time (in milliseconds), the code will only be executed once; 2, setInterval () function, used to repeat some code according to the specified period (in milliseconds).

The operating environment of this tutorial: windows7 system, javascript1.8.5 version, Dell G3 computer.

JavaScript timers, sometimes called "timers", are used to perform certain tasks after a specified period of time, similar to the alarm clock in our lives.

In JavaScript, we can use timers to delay the execution of some code or to repeat some code at regular intervals. For example, you can use a timer to regularly update advertisements on a page or display a real-time clock, and so on.

There are two ways to set timers in JavaScript, setTimeout () and setInterval (). The differences between them are as follows:

The method states that setTimeout () executes some code after the specified time (in milliseconds). The code will only execute setInterval () once to repeat the execution of some code in the specified period (milliseconds). The timer will not stop automatically unless the clearInterval () function is called to manually stop or close the browser window.

SetTimeout ()

The JS setTimeout () function is used to execute some code after a specified time, and the code is executed only once.

The syntax format of the JS setTimeout () function is as follows:

SetTimeout (code,millisec)

The parameters are described as follows:

Code is required. The JavaScript code string to be executed after the function to be called.

Millisec is required. The number of milliseconds to wait before executing the code.

The sample code is as follows:

JavaScript var myFun = function (str = 'JavaScript') {[xss_clean] (str + "

");}; setTimeout (myFun, 500, 'Hello'); setTimeout (myFun, 1000); setTimeout (function () {[xss_clean] (" timer)

");}, 1500) setTimeout (" [xss_clean] (\ "setTimeout ()\") ", 2000)

Run the above code with an interval of 500 milliseconds and output the following in turn:

HelloJavaScript timer setTimeout ()

SetInterval ()

The JS setInterval () function can define a timer that can be executed repeatedly, waiting for a specified interval for each execution.

The syntax format of the JS setInterval () function is as follows:

SetInterval (code,millisec [, "lang"])

The parameters are described as follows:

Code is required. The function to call or the code string to execute.

Millisec must. The interval in milliseconds between periodic execution or invocation of a code.

Tip: timers defined by the setInterval () function will not stop automatically unless you call the clearInterval () function to manually stop or close the browser window.

The sample code is as follows:

JavaScript

Var num = 1; var myFun = function () {document.getElementById ('one') [xss_clean] + = num + "; num +;}; setInterval (myFun, 500); setInterval (function () {var d = new Date (); document.getElementById (' two') [xss_clean] = d.toLocaleTimeString ();}, 1000)

The running results are as follows:

JS cancel timer

When you use setTimeout () or setInterval () to set a timer, both methods produce a timer with a unique ID,ID of a positive integer value, also known as a timer identifier, through which we can clear the timer corresponding to ID.

We can use the clearTimeout () or clearInterval () functions to clear timers created by the setTimeout () or setInterval () functions, respectively. To call the clearTimeout () or clearInterval () function, you need to provide the unique ID of the timer as a parameter. The sample code is as follows:

JavaScript

The current time is:

A prompt box pops up after 2 seconds

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