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JavaScript JavaScript and the DOM (Retiring) Traversing the DOM Sibling Traversal

Posted by Daniel Statsenko
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Daniel Statsenko
Full Stack JavaScript Techdegree Student 4,235 Points

One or more of the buttons do not affect their previous sibling paragraphs.

My code highlights the <p> element of the previous list item, however I keep getting the "One or more of the buttons do not affect their previous sibling paragraphs." error message. 

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

list.addEventListener('click', function(e) {
  if (e.target.tagName == 'BUTTON') {
    let li = e.target.parentNode;
    let prevLi = li.previousElementSibling;
    if (prevLi) {
      let p = prevLi.firstElementChild;
      p.className = 'highlight';
     }
    }
});
app.js 
var list = document.getElementsByTagName('ul')[0];

list.addEventListener('click', function(e) {
  if (e.target.tagName == 'BUTTON') {
    let li = e.target.parentNode;
    let prevLi = li.previousElementSibling;
    if (prevLi) {
      let p = prevLi.firstElementChild;
      p.className = 'highlight';
     }
    }
});
index.html 
<!DOCTYPE html>
<html>
    <head>
        <title>JavaScript and the DOM</title>
    </head>
    <link rel="stylesheet" href="style.css" />
    <body>
        <section>
            <h1>Making a Webpage Interactive</h1>
            <p>Things to Learn</p>
            <ul>
                <li><p>Element Selection</p><button>Highlight</button></li>
                <li><p>Events</p><button>Highlight</button></li>
                <li><p>Event Listening</p><button>Highlight</button></li>
                <li><p>DOM Traversal</p><button>Highlight</button></li>
            </ul>
        </section>
        <script src="app.js"></script>
    </body>
</html>

Mod edit: Fixed code markdown -- triple backticks need to be on their own line before and after code.

1 Answer

Rabin Gharti Magar
seal-mask
PLUS
.a{fill-rule:evenodd;}techdegree seal-36
Rabin Gharti Magar
Front End Web Development Techdegree Graduate 20,928 Points
Rabin Gharti Magar
.a{fill-rule:evenodd;}techdegree seal-36
Rabin Gharti Magar
Front End Web Development Techdegree Graduate 20,928 Points

Hey Daniel Statsenko,

For this challenge, you don't have to create any new variables. You simply use a previousElementSibling and add a class name.

Here's the final version:

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

list.addEventListener('click', function(e) {
  if (e.target.tagName == 'BUTTON') {
    e.target.previousElementSibling.classList.add('highlight');
  }
});

There are three things happening on the above code:

  1. Inside the parentheses of conditional statement e.target.tagName looks specifically for a button tag.
  2. Inside the code block if it matches, you simply use e.target along with previousElementSibling method which will look for button previous sibling which is <p> tag.
  3. Finally add the class name of highlight to <p> tags

To learn how event target works, check out this link: https://developer.mozilla.org/en-US/docs/Web/API/Event/target

Hope this helps!

Daniel Statsenko
.a{fill-rule:evenodd;}techdegree
Daniel Statsenko
Full Stack JavaScript Techdegree Student 4,235 Points

Thank you for your help Rabin :)