easy way to throttle async tasks

AsyncTaskThrottle.js

function AsyncTaskThrottle () {
    this._queued = null;
    this._busy = false;
}

AsyncTaskThrottle.prototype = {
    do: function (task) {
        if (!this._busy) {
            this._queued = task;
            return this._call();
        } else {
            this._queued = task;
        }
    },
                        
    _call: function () {
        if (this._busy || !this._queued) return;

        var self = this,
            task = this._queued;

        this._queued = null;
        this._busy = true;

        task(function () {
            self._busy = false;
            self._call();
        });
    }
};

var taskThrottle = new AsyncTaskThrottle();

setInterval(function () {
    taskThrottle.do(function (callback) {
        setTimeout(function () {
            console.log('called');
            callback();
        }, 500);
    });
}, 50)