reentrant.js

function reentrant(f, opts) {
    opts = $.extend({catchup: false});
    var state = {
        running: false,
        reentry: false
    };
    var rf = function() {
        if (state.running) {
            state.reentry = true;
            return;
        }
        state.running = true;
        var r = f.apply(this, arguments);
        if (state.reentry && opts.catchup) {
            setTimeout(rf, 0);
        }
        state.running = false;
        state.reentry = false;
        return r;
    };

    return rf;
}