單擊時，我試圖將一個類添加到錨標記。但是，當我嘗試使用e.classList.add('active-link');I'm trying to use the same method being used here時，我得到“添加”未定義。const links = document.querySelectorAll('#navbar__list li a');links.forEach(function(e) {    // e.addEventListener('scroll', function() {    //     e.preventDefault();    //     for (let i = 0; i < links.length; i++) {    //     }    // });    e.addEventListener('click', function(e) {        // first remove active_link and active-section class from all a and section elements        links.forEach(function(e) {             e.classList.remove('active-link');            //console.log(`#section${e.id}`);            //document.querySelector(`#section${e.id}`).classList.remove('active-section');        })        // add the active-class to the a element and active-section to the linked section        e.classList.add('active-link');       //document.querySelector(`#section${e.id}`).classList.add('active-section');    })});