9点击按钮修改valu属性

<input type="button" value="按钮" id="btn9">
        <script type="text/javascript">
            var btn9Obj=document.getElementById("btn9");
            btn9Obj.onclick=function(){
                this.value="lala";
                this.type="text";
                this.id="sa";
            };
        </script>