onHidden = function () {
        if (cc.eventManager && cc.game._eventHide)
            cc.eventManager.dispatchEvent(cc.game._eventHide);
    }
A string tool to construct a string with format string.
for example:
     cc.formatStr("a: %d, b: %b", a, b);
     cc.formatStr(a, b, c);
@returns {String}