利用数组和提取split（）方法来解决，供大家参考

<script type="text/javascript">

  var attime;

  function clock(){

    var time=new Date();

    var myarr=time.split(" ");

    attime=myarr[4];

    document.getElementById("clock").value = attime;

  }

  setInterval(clock,1000);

</script>