<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title></title> <style> *{ margin: 0; padding: 0; } </style> </head> <body> <p> <span class="m">10</span>" <span class="s">05</span> </p> <br /> <br /> <input type="button" value="开始" /> <script> var btn = document.querySelector('input'); var mText = document.querySelector('.m').innerHTML; var sText = document.querySelector('.s').innerHTML; var s var m m = goNumber(mText); s = goNumber(sText); var timer btn.onclick=function(){ if( this.value == '开始' ){ timer = setInterval(timeGo,1000); this.value = '暂停'; }else{ clearInterval(timer); this.value = '开始'; } } function timeGo(){ s-- if( s < 0 ){ if( m == 0 ){ clearInterval(timer); s++ }else{ s = 59 m-- if( m >= 0 && m < 10 ){ m = '0' + m; } document.querySelector('.m').innerHTML = m; } } if( s >= 0 && s < 10 ){ s = '0' + s; } document.querySelector('.s').innerHTML = s; } function goNumber(str){ var number = parseInt(str); return number; } </script> </body> </html>