javascript如何设置字体大小

<script>

    window.onload= function(){

        var oPtxt=document.getElementById("p1");

        var oBtn1=document.getElementById("Btn1");

        var oBtn2=document.getElementById("Btn2");

        var num = 14; /*定义一个初始变量*/

        oBtn1.onclick = function(){

            num++;

            oPtxt.style.fontSize=num+'px';

        };

        oBtn2.onclick = function(){

            num--;

            oPtxt.style.fontSize=num+'px';

        }

    }

</script>