// TODO
var arr = ['JavaScript', 'HTML', 'CSS'];
var node = [];
var list = document.getElementById('test-list');

for(var i=0; i<list.children.length; i++) {
    if(arr.indexOf(list.children[i].innerText) === -1) {
        node.push(list.children[i]);
    }
}

for(var i=0; i<node.length; i++) {
    list.removeChild(node[i]);
}