function fakeFetchCourses() {
  return new Promise(function (resolve) {
    setTimeout(function () {
      resolve(["DOM 获取元素", "事件监听", "异步基础"]);
    }, 800);
  });
}

const loadButton = document.getElementById("load-btn");
const statusText = document.getElementById("status-text");
const courseList = document.getElementById("course-list");

loadButton.addEventListener("click", function () {
  statusText.textContent = "加载中...";
  courseList.innerHTML = "";

  fakeFetchCourses()
    .then(function (courses) {
      courses.forEach(function (course) {
        const item = document.createElement("li");
        item.textContent = course;
        courseList.appendChild(item);
      });

      statusText.textContent = "加载完成";
    })
    .catch(function () {
      statusText.textContent = "加载失败";
    });
});