代码

function getCurrentTime() {
    var currentTime = new Date();
    var hours = currentTime.getHours();
    var minutes = currentTime.getMinutes();
    var seconds = currentTime.getSeconds();

    // 将单个的小时、分钟、秒如果小于10，在前面添加一个0
    hours = (hours < 10 ? "0" : "") + hours;
    minutes = (minutes < 10 ? "0" : "") + minutes;
    seconds = (seconds < 10 ? "0" : "") + seconds;

    // 拼接时间
    var currentTimeString = hours + ":" + minutes + ":" + seconds;

    // 在页面上显示时间
    document.getElementById("time").innerHTML = currentTimeString;
  }

效果