Help needed

I need more information to see what you are actually trying to achieve, but I did notice a syntax error over here

 let li = event.target.parentNode;

right now the 'e' in your function is your event so it should just be:

let li = e.target.parentNode.

Also, I'm not sure what you're trying to do with this line:

if(hightlight) {
      ul.insertBefore(hightlight, li);
    }

If you're just checking if a variable called 'hightlight' exists and trying to insert it before the 'ul' element you do not need the 'if statement' you can just use the code inside the if statement, it should look like this:

ul.insertBefore(hightlight, li);

If you need any more help, comment below this post.

I'm not clear on what's confusing you can you elaborate, also what are you trying to create with this code.

If you are confused about the 'event' and 'e' thing that I told you about, here's a more in-depth explanation: Basically your function parameter 'e' is a reference to the event object, so you should be typing in e.target.tagName, if you want to type in 'event' instead of 'e' you can change the parameter in your function from e to event.

Your altered code does not define 'hightlight' before calling it into the insertBefore method, you must first define 'hightlight.' The rest looks good, though!

What method are you trying to understand to use, I'd be happy to help!

I'm not sure what the objective is, but I'll give you a run-through of your code if it helps you to understand sibling traversal better.

var list = document.getElementsByTagName('ul')[0];

list.addEventListener('click', function(e) {
  if (e.target.tagName == 'BUTTON') {
    let li = event.target.parentNode;
    //let p = highlight.previousElementSibling;
    let hightlight = li.previousElementSibling;
    let ul = li.parentNode;
    if(hightlight){
      ul.insertBefore(hightlight, li);
    }
  }
});

Your if statement says: "if the user has clicked on the element with the tagName "BUTTON" execute the following:"

1st line: Creates a variable called 'li' which is the parent node of the element with the tagName "BUTTON"(in your HTML, the element which is the parent of the "BUTTON" element is assigned to the variable 'li,' which in this case, is your actual list item).

2nd line: Creates a variable called 'hightlight' which is the previousElementSibling of the element of your 'li' variable(remember your 'li' variable corresponds to a list item, which is the parent of the button which the user presses, which is the list item on top of the list item which the user has selected).

3rd line: you select the 'ul' which is the parentNode of the list item(this selects the actual 'ul').

Lines 4 and 5: You check if a variable called "highlight" exists, and if so, you insert highlight before the selected list item(I know had told you to change this, but now that I'm looking through your project more, this is actually better practice).

If you still need help, you are welcome to respond, I'm happy to help.