js 定时器

         <input type="text" id="textview">
    <input type="button" value="start" onclick="start_button()">
    <input type="button" value="end" onclick="end_button()">





   function beging() {

        var date = new Date();
        var hour = date.getHours();
        var fen = date.getMinutes();
        var miao = date.getSeconds();

        var gettime = [hour,"时",fen,"分",miao,"秒"].join("");

        var doc_text = document.getElementById("textview");
        doc_text.value = gettime ;

        }


        //给定时器添加每秒自动获取时间
        var ID ;
        function start_button() {

            if(ID===undefined){
                beging();
                ID = setInterval(beging,1000)
            }
        }

        //结束时间
        function end_button() {
            clearInterval(ID);
            ID = undefined;

        }