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[JavaScript] uses the setInterval () function for simple round robin. setinterval round robin
Polling is a way for the CPU to decide how to provide peripheral device services, also known as Programmed I/O ). The concept of the Round-Robin method is that the CPU regularly sends a query, asking each peripheral device in sequence whether or not they need the service. Once the service is completed, it then asks the next peripheral device and continues to repeat it. The polling method is easy to implement, but inefficient.
When using the setInterval function in JavaScript For simple round robin operations, you can determine a parameter value at any time, but you do not need to refresh the page, that is, you do not need to add <META HTTP-EQUIV = "Refresh" CONTENT = "5"> in the page header to Refresh the page.
I. Basic Objectives
You do not need the onChange () function to directly use the setInterval function for a simple round-robin operation. The content in the text box is not read every 0.5 seconds.
In fact, the principle is the same as that of the JavaScript clock. It takes the current time every second and then updates the text content once.
Ii. Production Process
The Code is as follows:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">The polling () function starts execution after the page is loaded. the synchronous () function is executed first, and then the synchronous () function is always executed every 0.5 seconds.
JAVASCRIPT setInterval operation<Html>
<Body>
<Div id = "one"> 5 </div>
<Script>
Var I = 5;
Var one = document. getElementById ("one ");
Var si = setInterval (function (){
One. innerText = I --;
If (I = 0) clearInterval (si );
}, 1000)
</Script>
</Body>
</Html>
How does javascript clear setInterval in another function?// The first floor and second floor are completely incorrect. In the timer call, it is show (). You have not declared this function and generate an incorrect timer. The code must have an error.
Var timer1 = null;
Function start (){
If (timer1)
Return;
Timer1 = setInterval ("test ()", 200 );
}
Function end (){
If (timer1)
{
ClearInterval (timer1 );
Timer1 = null;
}
}
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