JavaScript JavaScript and the DOM Traversing the DOM Getting All Children of a Node with children

Siddharth Pande
Siddharth Pande
9,044 Points

discussion about the use of appendChild with a forLoop

const toggleList = 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 listUl = listDiv.querySelector('ul');
const addItemInput = document.querySelector('input.addItemInput');
const addItemButton = document.querySelector('button.addItemButton');
const lis = listUl.children;

function attachListItemButtons(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 < lis.length; i += 1) {
  attachListItemButtons(lis[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.className == 'up') {
      let li = event.target.parentNode;
      let prevLi = li.previousElementSibling;
      let ul = li.parentNode;
      if (prevLi) {
        ul.insertBefore(li, prevLi);
      }
    }  
    if (event.target.className == 'down') {
      let li = event.target.parentNode;
      let nextLi = li.nextElementSibling;
      let ul = li.parentNode;
      if (nextLi) {
        ul.insertBefore(nextLi, li);
      }
    } 
  }
});

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

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

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

The code above creates buttons using javascript (and does other stuff too, but i want to focus on the creation of button) and works fine, but,

the code below (using the appendChild button in the loop causes a different behaviour and all the buttons are appended to only the last list item.

const toggleList = 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 listUl = listDiv.querySelector('ul');
const lis = listUl.children;
const addItemInput = document.querySelector('input.addItemInput');
const addItemButton = document.querySelector('button.addItemButton');


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.className == 'up') {
      let li = event.target.parentNode;
      let prevLi = li.previousElementSibling;
      let ul = li.parentNode;
      if (prevLi) {
        ul.insertBefore(li, prevLi);
      }
    }  
    if (event.target.className == 'down') {
      let li = event.target.parentNode;
      let nextLi = li.nextElementSibling;
      let ul = li.parentNode;
      if (nextLi) {
        ul.insertBefore(nextLi, li);
      }
    } 
  }
});

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

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

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

    var li;
    const btnUp = document.createElement('button');
    btnUp.className = "up";
    btnUp.textContent = "Up";

    const btnDown = document.createElement('button');
    btnDown.className = 'down';
    btnDown.textContent = 'Down';

    let btnRemove = document.createElement('button');
    btnRemove.className = "remove";
    btnRemove.textContent = "Remove";

  for (i = 0; i < lis.length; i += 1) {
   lis[i].appendChild(btnUp);
   lis[i].appendChild(btnDown);
   lis[i].appendChild(btnRemove);
  }

Please, please, please explain this to me.........

Siddharth Pande
Siddharth Pande
9,044 Points

Steven Parker I need some help here

1 Answer

Liam Clarke
MOD
Liam Clarke
Treehouse Moderator 19,187 Points

Hi Siddarth

This is because the const value of btnUp, btnDown, btnRemove are getting overwritten every time in your for loop.

So if you trace through your code you can actually see one by one they get set and then get removed until the loop finishes at the bottom.

Solution - Add the variables in the loop

  for (i = 0; i < lis.length; i += 1) {
    const btnUp = document.createElement('button');
    btnUp.className = "up";
    btnUp.textContent = "Up";
    const btnDown = document.createElement('button');
    btnDown.className = 'down';
    btnDown.textContent = 'Down';
    const btnRemove = document.createElement('button');
    btnRemove.className = "remove";
    btnRemove.textContent = "Remove";
    lis[i].appendChild(btnUp);
    lis[i].appendChild(btnDown);
    lis[i].appendChild(btnRemove);
  }

You can make this cleaner by separating this into a function. This will help with DRY coding but as for the question, you was overwriting each time you iterated over the loop

Good Luck