Javascript Reference - Window setInterval() Method
The setInterval() method calls a function at specified milliseconds.
setInterval() executes the code repeatedly at
specific time intervals until the interval is canceled or
the page is unloaded.
The setInterval() method accepts:
- the code to execute
- the milliseconds to wait between executions.
<!DOCTYPE HTML>
<html>
<body>
<script type="text/javascript">
setInterval(function() { <!--from w w w . ja va2 s . c o m-->
document.writeln("Hello world!");
}, 1000);
</script>
</body>
</html>Browser Support
 |
 |
 |
 |
 |
|
|---|---|---|---|---|---|
setInterval |
Yes | Yes | Yes | Yes | Yes |
Syntax
setInterval(function,milliseconds,lang)
Parameter Values
| Parameter | Description |
|---|---|
| function | Required. The function to call |
| milliseconds | Required. The intervals in milliseconds to execute the code |
| lang | Optional. JScript | VBScript | JavaScript |
Return Value
An integer ID value of the timer.
Example
The following code shows how to display the current time every second.
<!DOCTYPE html>
<html>
<body>
<p id="demo"></p>
<script>
var myVar = setInterval(function(){myTimer()}, 1000);
<!--from w w w. j a v a 2s. com-->
function myTimer() {
var d = new Date();
var t = d.toLocaleTimeString();
document.getElementById("demo").innerHTML = t;
}
</script>
</body>
</html>
The code above is rendered as follows:
Clear the timer
The setInterval() method returns an interval ID.
We can use the ID to cancel the interval with
clearInterval() method.
<!DOCTYPE HTML>
<html>
<body>
<script type="text/javascript">
var num = 0;
var max = 10;
var intervalId = null;
function incrementNumber() {
document.writeln(num++);
//if the max has been reached,
//cancel all pending executions
if (num == max) {
clearInterval(intervalId);
document.writeln("Done");
} <!-- w ww . j a v a 2 s. c o m-->
}
intervalId = setInterval(incrementNumber, 500);
</script>
</body>
</html>