window.wait

gistfile1.js

var wait = new function Wait() {
    var list = this.list = {};
    this.callback = function() { };
    this.add = function(s) {
        list[s] = true;
    };
    this.remove = function(s) {
        list[s] = false;
        if (this.ready()) {
            this.callback();
        }
    };
    this.ready = function() {
        for (key in list) {
            if (list[key]) {
                return false;
            }
        }
        return true;
    };
};