JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html lang="en">
  <head>
    <script src="/1-first-file.js"></script>
    <link rel="stylesheet" type="text/css" href="/styles.css" media="screen" />

    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Index</title>
  </head>
  <body>
    <div id="div1" class="regular">
      No strikethrough!
    </div>
  </body>
</html>

CSS

div {
  background-color: rgb(204, 47, 47);
  font-size: 25px;
  width: 250px;
  height: 250px;
}

#div1 {
  margin: 10px;
  text-align: center;
}


.regular {
  text-decoration: none;
}

.line-through {
  text-decoration: line-through;
}

JavaScript

document.addEventListener("click", (e) => {
  let closestDiv = e.target.closest("div");
  if (
    closestDiv &&
    closestDiv.id === "div1" &&
    closestDiv.className === "regular"
  ) {
    closestDiv.classList.add("line-through");
    closestDiv.innerText = "Strikethrough!";
  } else if (
    closestDiv &&
    closestDiv.id === "div1" &&
    closestDiv.className === "regular line-through"
  ) {
    closestDiv.innerText = "No strikethrough!";
    closestDiv.classList.remove("line-through");
  }
});