gistfile1.coffee

/*
 * Non-clamped setInterval
 * By Devon Govett (idea from sink.js)
 * MIT LICENSE
 */

(function() {
    
    var BlobBuilder = this.BlobBuilder || this.MozBlobBuilder || this.WebKitBlobBuilder,
        URL = this.URL || this.webkitURL,
        Worker = this.Worker;
    
    this.createTimer = function(fn, interval) {
        if (!BlobBuilder || !URL || !Worker)
            return setInterval(fn, interval);

        var bb = new BlobBuilder;
        bb.append("setInterval(function() { postMessage('ping'); }, " + interval + ");");
        var url = URL.createObjectURL(bb.getBlob());
        
        var worker = new Worker(url);
        worker.onmessage = fn;
        worker.url = url;
        
        return worker;
    }

    this.destroyTimer = function(timer) {
        if (timer.terminate) {
            timer.terminate();
            URL.revokeObjectURL(timer.url);
        }
        else {
            clearInterval(timer);
        }
    }
    
})();

usage.md

Ever wanted to have a non-clamped setInterval even in background tabs? Now you can! This works just like setInterval and clearInterval but in supported environments, uses a dynamically generated worker to run the timer, which avoids clamping in background tabs. No worries, if any of the necessary features to make this work are not supported, it will fall back to regular old setInterval. :)