const runButton = document.getElementById("run-btn");
const logList = document.getElementById("log-list");

function appendLog(text) {
  const item = document.createElement("li");
  item.textContent = text;
  logList.appendChild(item);
}

runButton.addEventListener("click", function () {
  logList.innerHTML = "";

  appendLog("开始执行");

  setTimeout(function () {
    appendLog("异步回调完成");
  }, 600);

  appendLog("同步代码结束");
});