main.js

function pageLoad() {
    document.getElementById("myForm").addEventListener("submit", processForm);
}
function processForm(event) {
    event.preventDefault();
    valid = true;
    let name = validate(document.getElementById("name").value,0);
    let drink = validate(document.getElementById("drink").value,0);
    let food = validate(document.getElementById("food").value,0);
    let location = validate(document.getElementById("eat-in").value,1);

    if (valid) {
        console.log("Name: "+name+", drink: "+drink+", food: "+food+", location: "+location);
        document.getElementById("name").value = "";
        document.getElementById("drink").value = "";
        document.getElementById("food").value = "";
        document.getElementById("eat-in").value = "";
        alert("Response processed (see dev console)");
    } else {
        alert("A text box is empty");
    }
}
function validate(string,type) {
    if (type===0) {
        if (string.length === 0) {
            valid = false;
        } else {
            return string;
        }
    }
}
let valid = true;