SOURCE

function welcome(username) {
    console.log('welcome ' + username);
}

function goodbye(username) {
    console.log('goodbye ' + username);
}

function wrapWithUsername(wrappedFunc) {
    let newFunc = () => {
        let username = localStorage.getItem('username');
        wrappedFunc(username);
    };
    return newFunc;
}

welcome = wrapWithUsername(welcome);
goodbye = wrapWithUsername(goodbye);

welcome();
goodbye();