var list = document.getElementById('test-list');
    for **(var i = 0; i < list.children.length;) **{
       // if (["JavaScript", "HTML", "CSS"].indexOf(list.children[i].innerText) == -1) {
        if (!["JAVASCRIPT", "HTML", "CSS"].includes(list.children[i].innerText.toUpperCase())) {
            list.removeChild(list.children[i]);
        } else {
            i++; //只有web有关的节点才++;
        }
    }