Question

I’m making a user count script with PHP and jquery and I would like to have a way of telling if the user is inactive.

$.mousemove(function(){
//get php to update time on user
});

but how should I set it so that it wouldn’t update every time it moved but once every 1 sec? Like this?

$.mousemove(function(){
//get php to update time on user
$.delay(1000);    
});

then I will also add a key up function with the same thing so that i can also tell if keyboard is active or not.

Answer 1

Hopefully this is self explanatory, and hopefully it works! This notifies the server immediately when the user moves the mouse, assuming the server hasn’t been notified in over a second, AND periodically.

We schedule activityNotification() to run every second (using something like jQuery timer or the setInterval(func, time) function), in order to handle the following timeline as responsively as possible:

• 0 ms: user moves mouse, server notified
  immediately
• 657 ms: user presses key,
  but too early to notify server of
  activity
• 1000 ms:
  activityNotification() runs as
  scheduled, sees that we have
  activity we have not notified the
  server about, notifies server
• 2000 ms: activityNotification() runs as
  scheduled, but nothing to inform server about
• 2124 ms: user moves mouse, server notified immediately as it’s been 1.124 seconds since the server was last notified

Code:

//Track the last activity you saw
var lastActivity = 0;

//Remember the last time you told the server about it
var lastNotified = 0;

//Determines how frequently we notify the server of activity (in milliseconds)
var INTERVAL = 1000;

function rememberActivity() {
    lastActivity = new Date().getTime();

    activityNotification();
}

function activityNotification() {
    if(lastActivity > lastNotified + INTERVAL) {
        //Notify the server
        /* ... $.ajax(); ... */

        //Remember when we last notified the server
        lastNotified = new Date().getTime();
    }
}

setInterval('activityNotification()', INTERVAL);

$.mousemove(function() {
    //Remember when we last saw mouse movement
    rememberActivity();
});

$.keyup(function() {
    //Remember when we last saw keyboard activity
    rememberActivity();
});

And remember, not all users will have JavaScript enabled, and this will cause serious battery drain on mobile devices.