<!doctype html> <html> <head> <meta charset="utf-8"> <title>网站首页</title> <style> </style> </head> <body> <form action="save.php" method="post" onSubmit="return check()"> 账号:<input type="text" id="account" name="account"> <input type="submit" value="提交"> </form> </body> </html> <script> function $(id){ return document.getElementById(id); } String.prototype.trim =function(){ return this.replace(/^\s+|\s+$/g,''); } function check(){ var aa=$('account'); var ac=aa.value.trim(); aa.value=ac; var p=/^[a-z]{6,12}$/i; if(!p.test(ac)){ alert('账号必须为6-12位英文字母'); aa.focus(); return false; } return true; } </script>