module design pattern example

(function() {
    let chatModule = (function() {
        let message = 'hi bro'

        function say() {
            console.log(message);
        }

        return {
            say: say
        }
    })();

    if(!window.chatModule) {
        window.chatModule = chatModule
    } else {
        console.error('bla bla bla')
    }
})(window)