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JavaScript JavaScript and the DOM (Retiring) Traversing the DOM Getting the First and Last Child

Vic Mercier
Vic Mercier
3,276 Points
Posted by Vic Mercier
Vic Mercier
3,276 Points

Challenge firstLi

For example, notice when I click on the Up button of the top list item,

nothing happens, because they can't go up any further than the top, right?

So using first element, child, you could remove the Up button here.

So the app doesn't have a nonfunctional button.

I don't know how to do that.

2 Answers

Steven Parker
Steven Parker
231,008 Points
Steven Parker
Steven Parker
231,008 Points

That was covered in the Removing Nodes video.

You might want to review that one. But be aware that if you remove the "up" button from the top item (and I assume the "down" button from the bottom), you'll need to recreate them if those items are moved with the other button.

As an alternative enhancement, I would recommend just setting the button's "disabled" property, which will change the visual appearance in a way most users will recognize as meaning "not active". Then you can just clear that property when the item is moved.

Vic Mercier
Vic Mercier
3,276 Points
Vic Mercier
Vic Mercier
3,276 Points

Can you show me your code

Vic Mercier
Vic Mercier
3,276 Points
Vic Mercier
Vic Mercier
3,276 Points 
const removeItemInput = document.querySelector("input.removeInput");
const toggleList = document.getElementById("togglelist");
const listDiv = document.querySelector(".list");
const listDivUl = document.querySelector("ul");
const myInput = document.querySelector("input.description");
const myP = document.querySelector("p.description");
const button  = document.querySelector("button.description");
const addItemInput = document.querySelector("input.addItemInput");
const addItemButton = document.querySelector("button.addItemButton");
const removeButton = document.querySelector("button.removeItemButton");
const lis = listDivUl.children;
function attachListItemsButton(li){
  //Up button
  let up = document.createElement("button");
  up.className = "up";
  up.textContent = "up";

  li.appendChild(up);
  //Down button
  let down = document.createElement("button");
  down.className = "down";
  down.textContent = "down";
  li.appendChild(down);
  //Remove button
  let remove = document.createElement("button");
  remove.className = "remove";
  remove.textContent = "remove";
  li.appendChild(remove);
}

listDivUl.addEventListener("click", (event) => {
if(event.target.tagName == "BUTTON"&& event.target.className == "remove"){
let li = event.target.parentNode;
let ul = li.parentNode;
ul.removeChild(li);
}
});
listDivUl.addEventListener("click", (event) => {
if(event.target.tagName == "BUTTON" && event.target.className == "up"){
let li = event.target.parentNode;
let previousLi = li.previousElementSibling;
let ul = li.parentNode;





if(previousLi ){
ul.insertBefore(li, previousLi);

}
}
});
listDivUl.addEventListener("click", (event) => {
if(event.target.tagName == "BUTTON" && 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";
}                            
                            });


button.addEventListener("click", () => {
myP.textContent = myInput.value+" : " ; 
myInput.value = "";
                        });

addItemButton.addEventListener("click", () => {

let ul = document.getElementsByTagName("ul")[0];
let li = document.createElement("li");
li.textContent = addItemInput.value;
let firstChild = ul.firstElementChild;

attachListItemsButton(li);

ul.appendChild(li);

let first = ul.firstElementChild;
let button = document.getElementsByClassName("up")[0];
first.removeChild(button);
addItemInput.value = "";                       
                        });

Is that better?

Steven Parker
Steven Parker
231,008 Points
Steven Parker
Steven Parker
231,008 Points

When posting code, always use the instructions for code formatting in the Markdown Cheatsheet pop-up below the "Add an Answer" area. :arrow_heading_down: Or watch this video on code formatting.

And here's the basic code for making a button disabled (and not):

var button = event.target;
button.disabled = true;   // button stops working and appears gray
button.disabled = false;  // button works again
Steven Parker
Steven Parker
231,008 Points
Steven Parker
Steven Parker
231,008 Points

A disabled button won't move, but it will look different (gray color) and will no longer respond to clicks.