index.js

"use strict";

function burgerClick() {
    const hamburger = document.querySelector('.hamburger');         // selects hamburger icon.
    const navLinks = document.querySelector('.nav-links');          // selects nav-links element
    const links = document.querySelectorAll(".nav-links li");       // selects all the li's in nav-links

    hamburger.addEventListener("click", function(event) {            // on click of the hamburger icon...
        navLinks.classList.toggle('open');                           // toggle the "open" style
        links.forEach(function(link) {
            link.classList.toggle('fade');
        });
    });
}

function setupEventHandlers() {
    burgerClick();
}

function initialize() {
    setupEventHandlers();
}

$(initialize);