my buttons are not working

const toggelList = document.getElementById('toggleList'); const listDiv = document.querySelector('.list'); const descriptionInput = document.querySelector('input.description'); const descriptionP = document.querySelector('p.description'); const descriptionButton = document.querySelector('button.description'); const addItemInput = document.querySelector('input.addItemInput'); const addItemButton = document.querySelector('button.addItemButton'); const listUl = listDiv.querySelector('ul'); const list = listUl.children;

function attachListItemButton (li){ let up = document.createElement('button'); up.className = 'up'; up.textContent = 'Up'; li.appendChild(up); let down = document.createElement('button'); down.className = 'down'; down.textContent = 'Down'; li.appendChild(down);

let remove = document.createElement('button'); remove.className = 'remove'; remove.textContent = 'Remove'; li.appendChild(remove);

}

for (let i = 0 ; i < list.length; i +=1){ attachListItemButton(list[i]);

}

listUl.addEventListener('click', (event) => {
        if(event.target.tagName == 'BUTTON'){ 
        if (event.target.ClassName == 'remove'){
        let li = event.target.parentNode;
        let ul =  li.parentNode;
        ul.removeChild(li);

        } 

        if(event.target.tagName == 'UP'){ 
        let li = event.target.parentNode;
        let prevli = li.previousElementSibling;
        let ul =  li.parentNode;
        if (prevli){
        ul.insertBefore(li,prevli);
        }
        }  
        if(event.target.tagName == 'DOWN'){ 
        let li = event.target.parentNode;
        let nextli = li.nextElementSibling;
        let ul =  li.parentNode;
         if (nextli){
        ul.insertBefore(nextli,li);
        }

        }  }       });

toggelList.addEventListener('click', () => { if(listDiv.style.display == 'none'){ toggelList.textContent = 'Hide list'; listDiv.style.display = 'block'; }else{ toggelList.textContent = 'Show list'; listDiv.style.display = 'none';

} });

descriptionButton.addEventListener('click', () => { descriptionP.textContent = descriptionInput.value + " :";
descriptionInput.value = ''; });

addItemButton.addEventListener('click', () => { let ul = document.getElementsByTagName('ul')[0]; let li = document.createElement('li'); li.textContent = addItemInput.value; attachListItemButton(li); ul.appendChild(li); addItemInput.value = ''; });