求一段简单的JAVASCRIPT的判断代码！

/*************************************************************
名称：isemail
功能：判断传入的变量值是否为合法的电子邮件地址
参数：email，源字符串；
返回：True或False，是否是邮件地址
说明：[email protected]
*************************************************************/
function isemail(email) {
var endvalue,allowstrlist;
endvalue=true;
allowstrlist="1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-.@";
if (email.lastIndexOf("@")==-1 || email.lastIndexOf(".")==-1) {
endvalue=false;
} else if (email.indexOf("@",email.indexOf("@")+1)!=-1 || email.indexOf(".",email.indexOf("@"))==-1) {
endvalue=false;
} else if (email.substr(0,1)=="@" || email.substr(0,1)=="." || email.substr(email.length-1,1)=="@" || email.substr(email.length-1,1)==".") {
endvalue=false;
}
for (var i=0;i<email.length;i++) {
if (allowstrlist.indexOf(email.substr(i,1))==-1) {
endvalue=false;
break;
}
}
return(endvalue);
}
/*********************************************************************************
* FUNCTION: isEmail
* PARAMETER: String (Email Address)
* RETURNS: TRUE if the String is a valid Email address
* FALSE if the passed string is not a valid Email Address
* EMAIL FORMAT: AnyName@EmailServer e.g; [email protected]
* @ sign can appear only once in the email address.
*********************************************************************************/
function isEmail (theStr) {
var atIndex = theStr.indexOf('@');
var dotIndex = theStr.indexOf('.', atIndex);
var flag = true;
theSub = theStr.substring(0, dotIndex+1) if ((atIndex < 1)||(atIndex != theStr.lastIndexOf('@'))||(dotIndex < atIndex + 2)||(theStr.length <= theSub.length))
{ return(false); }
else { return(true); }
}
/*********************************************************************************
* FUNCTION: isBetween
* PARAMETERS: val AS any value
* lo AS Lower limit to check
* hi AS Higher limit to check
* CALLS: NOTHING
* RETURNS: TRUE if val is between lo and hi both inclusive, otherwise false.
**********************************************************************************/
function isBetween (val, lo, hi) {
if ((val < lo) || (val > hi)) { return(false); }
else { return(true); }
}/*********************************************************************************
* FUNCTION: isDate checks a valid date
* PARAMETERS: theStr AS String
* CALLS: isBetween, isInt
* RETURNS: TRUE if theStr is a valid date otherwise false.
**********************************************************************************/
function isDate (theStr) {
var the1st = theStr.indexOf('-');
var the2nd = theStr.lastIndexOf('-');

if (the1st == the2nd) { return(false); }
else {
var y = theStr.substring(0,the1st);
var m = theStr.substring(the1st+1,the2nd);
var d = theStr.substring(the2nd+1,theStr.length);
var maxDays = 31;

if (isInt(m)==false || isInt(d)==false || isInt(y)==false) {
return(false); }
else if (y.length < 4) { return(false); }
else if (!isBetween (m, 1, 12)) { return(false); }
else if (m==4 || m==6 || m==9 || m==11) maxDays = 30;
else if (m==2) {
if (y % 4 > 0) maxDays = 28;
else if (y % 100 == 0 && y % 400 > 0) maxDays = 28;
            else maxDays = 29;
}
if (isBetween(d, 1, maxDays) == false) { return(false); }
else { return(true); }
}
}
/********************************************************************************
*   FUNCTION:       Compare Date! Which is the latest!
*   PARAMETERS:     lessDate,moreDate AS String
*   CALLS:          isDate,isBetween
*   RETURNS:        TRUE if lessDate<moreDate
*********************************************************************************/
function isComdate (lessDate , moreDate)
{
if (!isDate(lessDate)) { return(false);}
if (!isDate(moreDate)) { return(false);}
var less1st = lessDate.indexOf('-');
var less2nd = lessDate.lastIndexOf('-');
var more1st = moreDate.indexOf('-');
var more2nd = moreDate.lastIndexOf('-');
var lessy = lessDate.substring(0,less1st);
var lessm = lessDate.substring(less1st+1,less2nd);
var lessd = lessDate.substring(less2nd+1,lessDate.length);
var morey = moreDate.substring(0,more1st);
var morem = moreDate.substring(more1st+1,more2nd);
var mored = moreDate.substring(more2nd+1,moreDate.length);
var Date1 = new Date(lessy,lessm,lessd);
var Date2 = new Date(morey,morem,mored);
if (Date1>Date2) { return(false);}
return(true);

}/*********************************************************************************
* FUNCTION isEmpty checks if the parameter is empty or null
* PARAMETER str AS String
**********************************************************************************/
function isEmpty (str) {
    if ((str==null)||(str.length==0)) return true;
    else return(false);
}
/*********************************************************************************
* FUNCTION isAllEmpty checks if all the character is empty or null
* PARAMETER str AS String
**********************************************************************************/
function isAllEmpty (str)
{
if ((str==null)||(str.length==0)) return true;
else
{
for (var i=0; i<str.length; i++)
{
if (str.substring(i,i+1)!=" ") return false;
}
return true
}
}/*********************************************************************************
* FUNCTION: isInt
* PARAMETER: theStr AS String
* RETURNS: TRUE if the passed parameter is an integer, otherwise FALSE
* CALLS: isDigit
**********************************************************************************/
function isInt (theStr) {
var flag = true; if (isEmpty(theStr)) { flag=false; }
else
{ for (var i=0; i<theStr.length; i++) {
if (isDigit(theStr.substring(i,i+1)) == false) {
flag = false; break;
}
}
}
return(flag);
}/*********************************************************************************
* FUNCTION: isReal
* PARAMETER: heStr AS String
    decLen AS Integer (how many digits after period)
* RETURNS: TRUE if theStr is a float, otherwise FALSE
* CALLS: isInt
**********************************************************************************/
function isReal (theStr, decLen) {
var dot1st = theStr.indexOf('.');
var dot2nd = theStr.lastIndexOf('.');
var OK = true;
if (isEmpty(theStr)) return false; if (dot1st == -1) {
if (!isInt(theStr)) return(false);
else return(true);
}
else if (dot1st != dot2nd) return (false);
else if (dot1st==0) return (false);
else {
var intPart = theStr.substring(0, dot1st);
var decPart = theStr.substring(dot2nd+1); if (decPart.length > decLen) return(false);
else if (!isInt(intPart) || !isInt(decPart)) return (false);
else if (isEmpty(decPart)) return (false);
else return(true);
}
}/*********************************************************************************
* FUNCTION: isEmail
* PARAMETER: String (Email Address)
* RETURNS: TRUE if the String is a valid Email address
* FALSE if the passed string is not a valid Email Address
* EMAIL FORMAT: AnyName@EmailServer e.g; [email protected]
* @ sign can appear only once in the email address.
*********************************************************************************/
function isEmail (theStr) {
var atIndex = theStr.indexOf('@');
var dotIndex = theStr.indexOf('.', atIndex);
var flag = true;
theSub = theStr.substring(0, dotIndex+1) if ((atIndex < 1)||(atIndex != theStr.lastIndexOf('@'))||(dotIndex < atIndex + 2)||(theStr.length <= theSub.length))
{ return(false); }
else { return(true); }
}

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求一段简单的JAVASCRIPT的判断代码！

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