JavaScript Timing Events

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JavaScript can be executed in time-intervals.

This is called timing events.


JavaScript Timing Events



With JavaScript, it is possible to execute some code after a specified time-interval. This is called timing events.
It's very easy to time events in JavaScript. The two key methods that are used are:

• setTimeout() - executes a code some time in the future
• clearTimeout() - cancels the setTimeout()

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


The setTimeout() Method

Syntax

var t=setTimeout("javascript statement",milliseconds); The setTimeout() method returns a value - In the statement above, the value is stored in a variable called t. If you want to cancel this setTimeout(), you can refer to it using the variable name.
The first parameter of setTimeout() is a string that contains a JavaScript statement. This statement could be a statement like "alert('5 seconds!')" or a call to a function, like "alertMsg()".


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



Note: There are 1000 milliseconds in one second.
Example

When the ****on is clicked in the example below, an alert box will be displayed after 5 seconds.


Example

onClick="timedMsg()" />

Example - Infinite Loop

To get a timer to work in an infinite loop, we must write a function that calls itself. In the example below, when the ****on is clicked, the input field will start to count (for ever), starting at 0:


Example

The clearTimeout() Method

Syntax

clearTimeout(setTimeout_variable)

Example

The example below is the same as the "Infinite Loop" example above. The only difference is that we have now added a "Stop Count!" ****on that stops the timer:


Example

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More Examples

Another simple timing

Click on the ****on above. The input field will tell you when two, four, and six seconds have passed.

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A clock created with a timing event