var parent = document.getElementById('test-list');
for (var i = parent.children.length - 1; i >= 0; i--)
{
     if (parent.children[i].innerText !== 'JavaScript' && parent.children[i].innerText !== 'HTML' && parent.children[i].innerText !== 'CSS')
     {
         parent.removeChild(parent.children[i]);
     }
}