2-dom/mouse-events/selectableList.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <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>Document</title>
    <style>
      .selected {
        background: #0f0;
      }

      li {
        cursor: pointer;
      }
    </style>
  </head>
  <body>
    선택하고자 하는 요소를 클릭하세요.
    <br />

    <ul id="ul">
      <li>React</li>
      <li>Angular</li>
      <li>Vue</li>
      <li>Svelte</li>
      <li>Blazor</li>
    </ul>

    <script>
      ul.onclick = function (event) {
        if (event.target.tagName != "LI") return;

        if (event.ctrlKey || event.metaKey) {
          toggleSelect(event.target);
        } else {
          singleSelect(event.target);
        }
      };

      // 요소를 클릭할 때 불필요하게 선택되지 않도록 방지
      ul.onmousedown = function () {
        return false;
      };

      function toggleSelect(li) {
        li.classList.toggle("selected");
      }

      function singleSelect(li) {
        let selected = ul.querySelectorAll(".selected");
        for (let elem of selected) {
          elem.classList.remove("selected");
        }
        li.classList.add("selected");
      }
    </script>
  </body>
</html>