JavaScriptisNaN检测变量是否为非数字实现方法。
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="https://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>无标题文档</title> <script> window.onload=function () { var oTxt1=document.getElementById('txt1'); var oTxt2=document.getElementById('txt2'); var oBtn=document.getElementById('btn1'); oBtn.onclick=function () { var num=parseInt(oTxt1.value)+parseInt(oTxt2.value); if(isNaN(num)) { alert('您输入的有误'); } else { alert(num); } }; }; </script> </head> <body> <input id="txt1" type="text" /> <input id="txt2" type="text" /> <input id="btn1" type="button" value="求和" /> </body> </html>