Adding Class in Java Script

Question

I have been trying seventy-eleven ways to add a class of 'highlight' to the immediate sibling of each button but I am encountering a consistent error of reading my last element as 'null'. I am truly stuck here.

app.js

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

list.addEventListener('click', function(e) {
  if (e.target.tagName == 'BUTTON') {
    let btn = event.target.parentNode;
    let p = btn.previousElementSibling;
    //let li = p.parentNode;
    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>

Answer 1 · 2020-10-04T17:52:42Z

October 4, 2020 5:52pm

seemed to accept

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

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

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Theresa Greene

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Adding Class in Java Script

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Simon Coates

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