如何在javascript中连续执行代码？

Question

I have a HTML-file and a PHP-file. The index.php displays a value which gets transferred to the servo.php. The servo.php writes the value in a file called /dev/servoblaster.

Currently the value only gets displayed if i click the button with my function. I would like that the value is displayed and sent continuously and not by the press of a button.

The two files can you find here: servo.php index.html

The function: (You will find it also in the HTML-file)

    function tilt() { var tilt = document.getElementById("tiltRange").value;
                      document.getElementById("tilt_Range").innerHTML = tilt;
                      var xhttp = new XMLHttpRequest();
                      xhttp.open("GET", "servo.php?dir=P1-11=" + tilt, true);
                      xhttp.send();
                    }

The body tag of the HTML-file:

    <button onclick="tilt()">Tilt</button>

    <input type="range" id="tiltRange" value="140" max="170" min="60">

    <text id="tilt_Range"></text>

Answer 1

You could use setInterval to call your script every n seconds:

setInterval(tilt, 5000); 

Will call tilt() every 5 seconds...

EDIT:

Added clearInterval example:

var doIt = setInterval(tilt, 5000);

You can then clear / stop it like so:

clearInterval(doIt) 

So you should assign a click handler to your "stop" button, that calls the clearInterval.

Answer 2

You can use setInterval to execute any code at certain time interval.

 setInterval(function () {
           document.getElementById("tiltRange").value;
                          document.getElementById("tilt_Range").innerHTML = tilt;
                          var xhttp = new XMLHttpRequest();
                          xhttp.open("GET", "servo.php?dir=P1-11=" + tilt, true);
                          xhttp.send();

        },30000);

Answer 3

The answer by "Dhara Parmar" on this page worked for me.

I needed a scroll event trigger, such as when a user scroll downs to a web page of a certain position, an event would occur, such as a pop out or an alert message.

Here is an example:

setInterval(function () 
    {
        if ($(window).scrollTop() > 1200) // at what scroll position 
            {
                alert("hello");
            }

    }, 10); // time repetition interval in milliseconds

Answer 4

You could you use setInterval in this case, using the following syntax:

var interval = setInterval(function () 
{
    var tilt = document.getElementById("tiltRange").value;
               document.getElementById("tilt_Range").innerHTML = tilt;
               var xhttp = new XMLHttpRequest();
               xhttp.open("GET", "servo.php?dir=P1-11=" + tilt, true);
               xhttp.send();
}, 5000);

And when you want to stop it from doing that action, simply do:

clearInterval(interval);

Hope that helped :) Let me know if that's not the case