1.点击减小按钮，文字变小
2.点击增加按钮，文字变大
<!DOCTYPE HTML> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>无标题文档</title> <script> window.onload = function (){ var oBtn1 = document.getElementById('btn1'); var oBtn2 = document.getElementById('btn2'); var oP = document.getElementById('p1'); var num = 14; oBtn1.onclick = function (){ num -= 2; oP.style.fontSize = num + 'px'; // JS 不允许出现"-" // padding-top paddingTop // margin-left marginLeft }; oBtn2.onclick = function (){ // num = num + 2; num += 2; oP.style.fontSize = num + 'px'; // JS 不允许出现“-“ }; }; </script> </head> <body>