Javascript verification function

/**
* DHTML date validation script.
*/
// Declaring valid date character, minimum year and maximum year
VaR dtch = "-";
VaR minyear = 1900;
VaR maxyears = 2100;
Function isinteger (s ){
VaR I;
For (I = 0; I <S. length; I ++ ){
// Check that current character is number.
VaR c = S. charat (I );
If (C <"0") | (C> "9") return false;
}
// All characters are numbers.
Return true;
}
Function stripcharsinbag (S, bag ){
VaR I;
VaR returnstring = "";
// Search through string's characters one by one.
// If character is not in bag, append to returnstring.
For (I = 0; I <S. length; I ++ ){
VaR c = S. charat (I );
If (bag. indexof (c) =-1) returnstring + = C;
}
Return returnstring;
}
Function daysinfebruary (year ){
// February has 29 days in any year evenly divisible by four,
// Snapshot t for Centurial years which are not also divisible by 400.
Return (Year % 4 = 0 )&&((! (Year % 100 = 0) | (Year % 400 = 0 )))? 29: 28 );
}
Function daysarray (n ){
For (VAR I = 1; I <= N; I ++ ){
This [I] = 31
If (I = 4 | I = 6 | I = 9 | I = 11) {This [I] = 30}
If (I = 2) {This [I] = 29}
}
Return this
}
Function isdate (dtstr ){
VaR daysinmonth = daysarray (12)
VaR pos1 = dtstr. indexof (dtch)
VaR pos2 = dtstr. indexof (dtch, pos1 + 1)
VaR stryear = dtstr. substring (0, pos1)
VaR strmonth = dtstr. substring (pos1 + 1, pos2)
VaR strday = dtstr. substring (pos2 + 1)
Stryr = stryear
 
VaR temstrday = "";
VaR temstrmonth = "";
// Alert (strmonth. Length );
If (strday. charat (0) = "0" & strday. length> 1) temstrday = strday. substring (1)
If (strmonth. charat (0) = "0" & strmonth. length> 1) temstrmonth = strmonth. substring (1)
 
For (VAR I = 1; I <= 3; I ++ ){
If (stryr. charat (0) = "0" & stryr. length> 1) stryr = stryr. substring (1)
}
Month = parseint (temstrmonth)
Day = parseint (temstrday)
Year = parseint (stryr)
If (pos1 =-1 | pos2 =-1 ){
Controlsubmit = false;
Alert ("Time Format: 2006-09-03 ")
Return;
}
If (strmonth. length! = 2 | month <1 | month> 12 ){
Controlsubmit = false;
Alert ("enter a valid month, for example, 02 ")
Return;
}
If (strday. length! = 2 | day <1 | day> 31 | (month = 2 & day> daysinfebruary (year) | day> daysinmonth [month]) {
Controlsubmit = false;
Alert ("enter a valid day, for example, 02 ")
Return;
}
If (stryear. length! = 4 | year = 0 | year <minyear | year> maxyear ){
Controlsubmit = false;
Alert ("Please enter a 4-digit year between" + minyear + "and" + maxyear + ")
Return;
}
If (dtstr. indexof (dtch, pos2 + 1 )! =-1 | isinteger (stripcharsinbag (dtstr, dtch) = false ){
Controlsubmit = false;
Alert ("enter a valid time format, for example, 2006-09-03 ")
Return;
}
Controlsubmit = true;
}