<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <style>
      ul {
        padding: 0;
        margin: 0;
        list-style: none;
      }

      .options li {
        float: left;
        width: 100px;
        height: 40px;
        line-height: 40px;
        text-align: center;
        border: solid 1px #ddd;
      }

      .items li {
        width: 405px;
        height: 405px;
        display: none;
        border: solid 1px #ddd;
      }
    </style>
  </head>
  <body>
    <ul class="options">
      <li data-type="0" style="background-color: #25bb9b">题库</li>
      <li data-type="1">面试</li>
      <li data-type="2">学习</li>
      <li data-type="3">求职</li>
    </ul>
    <ul class="items">
      <li style="display: block">牛客题库，包含编程题、选择题等</li>
      <li>为你的面试提供一站式服务</li>
      <li>校招学习来牛客</li>
      <li>求职中有什么难题，可以联系我们</li>
    </ul>

    <script>
      var options = document.querySelector(".options");
      var optionItems = [].slice.call(document.querySelectorAll(".options li"));
      var items = [].slice.call(document.querySelectorAll(".items li"));
      // 补全代码
      options.onclick = function (e) {
        for (let i = 0, len = optionItems.length; i < len; i++) {
          optionItems[i].style.backgroundColor = "";
          items[i].style.display = "none";
        }
        optionItems[e.target.dataset.type].style.backgroundColor = "#25bb9b";
        items[e.target.dataset.type].style.display = "block";
      };
    </script>
  </body>
</html>

先重置其他的样式 在给带自定义属性的点击选项添加样式