Michael Watson Michael Watson - 6 months ago 38
Javascript Question

Pausing setInterval when page/ browser is out of focus

I have a simple slideshow that I've made on a client's homepage, using setInterval to time the rotations.

To prevent browsers from screwing up setInterval when the page isn't in focus (another tab is being viewed, or another programme), I'm using:

function onBlur() {
clearInterval(play);
};

function onFocus() {

mySlideRotateFunction();

};

if (/*@cc_on!@*/false) {
document.onfocusin = onFocus;
document.onfocusout = onBlur;
} else {
window.onfocus = onFocus;
window.onblur = onBlur;
}


Where mySlideRotateFunction sets the setInterval and runs some jQuery. While this works the majority of the time, I find that, on occasion, it appears as though onBlur hasn't run, and when I return to the page the timings have 'built up' and the rotations go crazy.

I can't quite determine a cause as to why this happens on occasion, and not on others.

My question- is there a problem with my code, and does anyone have a better suggestion for 'pausing' setInterval when browser window is out of focus?

Thanks

Answer

Try something like this:

var myInterval;
var interval_delay = 500;
var is_interval_running = false; //Optional

$(document).ready(function () {
    $(window).focus(function () {
        clearInterval(myInterval); // Clearing interval if for some reason it has not been cleared yet
        if  (!is_interval_running) //Optional
            myInterval = setInterval(interval_function, interval_delay);
    }).blur(function () {
        clearInterval(myInterval); // Clearing interval on window blur
        is_interval_running = false; //Optional
    });
});

interval_function = function () {
     is_interval_running = true; //Optional
     // Code running while window is in focus
}

Some testing done in IE9 and FF6