set default value in js .

kadang2 kita akan ambik value dari user and maybe kita expect value yg betul dari user . but dalam setengah keadaan user ni ada yg bangang kan tak supply apa2. contoh mudah dari aku kali ni

document.addEventListener('DOMContentLoaded', () => {
    const submitBtn = document.getElementById('submit-btn');

    if (submitBtn) {
        submitBtn.addEventListener('click', () => {
            greet(tanya());
        });
    } else {
        console.error("Button with ID 'submit-btn' not found.");
    }
});

const default_nama = 'guest';

const tanya = function () {
    const selection = prompt('please enter your name: ', '');
    if(selection === null || selection.trim() === ''){
        return;
    }
    return selection;
}

const greet = (asktanya = default_nama)   => {
    !asktanya &&  asktanya.trim() === ''? console.log(`hello ${default_nama}`) : console.log(`welcome ${asktanya}`);

}