W3Schools.com

JavaScript Timing Events


1
2
3
4
5
6
7
8
9
10
11
12

JavaScript can be executed in time-intervals.

This is called timing events.


JavaScript Timing Events

With JavaScript, it is possible to execute some code at specified time-intervals. This is called timing events.

It's very easy to time events in JavaScript. The two key methods that are used are:

  • setInterval() - executes a function, over and over again, at specified time intervals
  • setTimeout() - executes a function, once, after waiting a specified number of milliseconds

Note: The setInterval() and setTimeout() are both methods of the HTML DOM Window object.


The setInterval() Method

The setInterval() method will wait a specified number of milliseconds, and then execute a specified function, and it will continue to execute the function, once at every given time-interval.

Syntax

setInterval("javascript function",milliseconds);

The first parameter of setInterval() should be a function.

The second parameter indicates the length of the time-intervals between each execution.

Note: There are 1000 milliseconds in one second.

Example

Alert "hello" every 3 seconds:

setInterval(function(){alert("Hello")},3000);

Try it yourself »

The example show you how the setInterval() method works, but it is not very likely that you want to alert a message every 3 seconds.

Below is an example that will display the current time. The setInterval() method is used to execute the function once every 1 second, just like a digital watch.

Example

Display the current time:

function myFunction()
{
setInterval(function(){myTimer()},1000);
}

function myTimer()
{
var d=new Date();
var t=d.toLocaleTimeString();
document.getElementById("demo").innerHTML=t;
}

Try it yourself »

How to Stop the Execution?

The clearInterval() method is used to stop further executions of the function specified in the setInterval() method.

Syntax

clearInterval(intervalVariable)

To be able to use the clearInterval() method, you must use a global variable when creating the interval method:

myVar=setInterval("javascript function",milliseconds);

Then you will be able to stop the execution by calling the clearInterval() method.

Example

Same example as above, but we have added a "Stop the timer" button:

var myVar;

function myFunction()
{
myVar=setInterval(function(){myTimer()},1000);
}

function myTimer()
{
var d=new Date();
var t=d.toLocaleTimeString();
document.getElementById("demo").innerHTML=t;
}

function myStopFunction()
{
clearInterval(myVar);
}

Try it yourself »

The setTimeout() Method

Syntax

setTimeout("javascript function",milliseconds);

The setTimeout() method will wait the specified number of milliseconds, and then execute the specified function.

The first parameter of setTimeout() should be a function.

The second parameter indicates how many milliseconds, from now, you want to execute the first parameter.

Example

Wait 3 seconds, then alert "Hello":

setTimeout(function(){alert("Hello")},3000);

Try it yourself »

How to Stop the Execution?

The clearTimeoutl() method is used to stop the execution of the function specified in the setTimeout() method.

Syntax

clearTimeout(timeoutVariable)

To be able to use the clearTimeout() method, you must use a global variable when creating the timeout method:

myVar=setTimeout("javascript function",milliseconds);

Then, if the function has not allready being executed, you will be able to stop the execution by calling the clearTimeout() method.

Example

Same example as above, but we have added a "Stop the alert" button:

var myVar;

function myFunction()
{
myVar=setTimeout(function(){alert("Hello")},3000);
}

function myStopFunction()
{
clearTimeout(myVar);
}

Try it yourself »

Examples

More Examples

Another simple timing

A clock created with a timing event




W3Schools Certification

W3Schools' Online Certification

The perfect solution for professionals who need to balance work, family, and career building.

More than 10 000 certificates already issued!

Get Your Certificate »

The HTML Certificate documents your knowledge of HTML.

The CSS Certificate documents your knowledge of advanced CSS.

The JavaScript Certificate documents your knowledge of JavaScript and HTML DOM.

The jQuery Certificate documents your knowledge of jQuery.

The XML Certificate documents your knowledge of XML, XML DOM and XSLT.

The ASP Certificate documents your knowledge of ASP, SQL, and ADO.

The PHP Certificate documents your knowledge of PHP and SQL (MySQL).

WEB HOSTING
Best Web Hosting
PHP MySQL Hosting
Best Hosting Coupons
UK Reseller Hosting
Cloud Hosting
Top Web Hosting
$3.98 Unlimited Hosting
Premium Website Design
WEB BUILDING
Download XML Editor
FREE Website BUILDER
CREATE HTML Websites
EASY WEBSITE BUILDER
W3SCHOOLS EXAMS
Get Certified in:
HTML, CSS, JavaScript, XML, PHP, and ASP
W3SCHOOLS BOOKS
New Books:
HTML, CSS
JavaScript, and Ajax
STATISTICS
Browser Statistics
Browser OS
Browser Display
SHARE THIS PAGE


Оригинални текст