I would like to inquire about JavaScript return.

<script>
function showMovie(age) {
    //Exit if checkAge return value is false
    if (!checkAge(age)) { 
        return alert ('Error');
    //The return value of checkAge is true
    } } else { 
        alert('movie screening');
    }
}

function checkAge(age) {
    if (age > 18) {
        return true; 
    } } else {
        //Return false if you do not agree
        Did you get the consent of your guardian?'); 
    }
}

function init() {
    letage = prompt ('Please tell me your age');
    showMovie();
}
init();
</script>