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C # tutorial
JavaScript can be executed in time-intervals.This is called timing events
The window
object allows execution of code at specified time intervals.
These time intervals are called timing events.
The two key methods to use with JavaScript are:
setTimeout(function, milliseconds
)setInterval(function, milliseconds
)The setTimeout()
and setInterval()
are both methods of the HTML DOM Window object.
The window.setTimeout()
method can be written without the window prefix.
The first parameter is a function to be executed.
The second parameter indicates the number of milliseconds before execution.
Click a button. Wait 3 seconds, and the page will alert "Hello":
<button onclick="setTimeout(myFunction, 3000)">Try it</button>
<script>
function myFunction() {
alert('Hello');
}
</script>
The clearTimeout()
method stops the execution of the function
specified in setTimeout().
The window.clearTimeout()
method can be written without the window prefix.
The clearTimeout()
method uses the variable
returned from setTimeout()
:
If the function has not already been executed, you can stop the execution by calling the clearTimeout()
method:
Same example as above, but with an added "Stop" button:
<button onclick="myVar = setTimeout(myFunction, 3000)">Try it</button>
<button onclick="clearTimeout(myVar)">Stop it</button>
The setInterval()
method repeats a given function at every given
time-interval.
The window.setInterval()
method can be written without the window prefix.
The first parameter is the function to be executed.
The second parameter indicates the length of the time-interval between each execution.
This example executes a function called "myTimer" once every second (like a digital watch).
Display the current time:
setInterval(myTimer, 1000);
function myTimer() {
const d = new Date();
document.getElementById("demo").innerHTML = d.toLocaleTimeString();
}
There are 1000 milliseconds in one second.
The clearInterval()
method stops the executions of the function
specified in the setInterval() method.
The window.clearInterval()
method can be written without the window prefix.
The clearInterval()
method uses the variable returned from setInterval()
:
Same example as above, but we have added a "Stop time" button:
<p id="demo"></p>
<button onclick="clearInterval(myVar)">Stop time</button>
<script>
let myVar = setInterval(myTimer, 1000);
function myTimer() {
const d = new Date();
document.getElementById("demo").innerHTML = d.toLocaleTimeString();
}
</script>