JS代码
<script> //长度必须在6~20位之间 //开头不能为数字 //只能包含小写字母和数字 //数字:48~57 //小写字母:97~122 //innerHTML function fnLogin(){ var oUname = document.getElementById("uname"); var oUpass = document.getElementById("upass"); var oError = document.getElementById("error_box"); var isNotError = true; if(oUname.value.length > 20 || oUname.value.length < 6){ oError.innerHTML = "用户名长度必须在6~20位之间"; isNotError = false; return; }else if(oUname.value.charCodeAt(0) >= 48 && oUname.value.charCodeAt(0) <= 57){ oError.innerHTML = "用户名开头不能为数字"; isNotError = false; return; }else{ for(var i=0; i<oUname.value.length; i++){ if((oUname.value.charCodeAt(i) > 122 || oUname.value.charCodeAt(i) < 97) && (oUname.value.charCodeAt(i) > 57 || oUname.value.charCodeAt(i) < 48)){ oError.innerHTML = "用户名只能包含小写字母和数字"; isNotError = false; return; } } } if(oUpass.value.length > 20 || oUpass.value.length < 6){ oError.innerHTML = "密码长度必须在6~20位之间"; isNotError = false; return; } oError.innerHTML = "登录成功"; } </script>