<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>Document</title> </head> <body> <button id="add">放大</button> <button id="min">缩小</button> <div id="txt">陋室铭 斯是陋室惟吾德馨</div> <script> var add = document.getElementById(‘add‘); var min = document.getElementById(‘min‘); var txt = document.getElementById(‘txt‘); // 放大按钮 var num = 16; add.onclick = function(){ num +=2; // 等同于num = num + 2 console.log(num); if(num >= 40){ num = 40; } txt.style.fontSize = num + ‘px‘; } // 缩小按钮 min.onclick = function(){ num -= 2; if(num <= 12){ num = 12; } txt.style.fontSize = num + ‘px‘; } </script> </body> </html>
原文：https://www.cnblogs.com/shihaiying/p/13229758.html