waitFor.js

waitFor: function (config) {
    // Optional
    var context = config.context || window,
        interval = config.interval || 50,
        timeOut = config.timeOut || 2000,
        expire = config.expire || function(){};

    // Required
    var varName = config.varName,
        callback = config.callback;

    // Local
    var timeOutId,
        expireId;

    if (varName in context && !$.isEmptyObject(context[varName])) {
        callback(context[varName]);
    } else {
        !function lookUp () {
            timeOutId = setTimeout(function () {
                if (varName in context && !$.isEmptyObject(context[varName])){
                    callback(context[varName]);
                    clearTimeout(expireId);
                } else {
                    lookUp();
                }
            }, interval);
        }();

        if (config.timeOut !== 0)
            expireId = setTimeout(function () {
                clearTimeout(timeOutId);
                expire();
            }, timeOut);
    }
}