function isEmpty(field) {
    var trimmed = trim(field.value);

    if (trimmed == "") {
        return true;
    } else {
        return false;
    }
}

function trim(inValue) {
    return inValue.replace(/^\s+|\s+$/g, '');
}

function appendError(error, field) {
    var result = "";

    if (error == "") {
        result = error + field.id;
    } else {
        result = error + ", " + field.id;
    }

    return result;
}

var dtCh= "/";
var minYear=1900;
var maxYear=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,
    // EXCEPT 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 strMonth = dtStr.substring(0,pos1);
	var strDay = dtStr.substring(pos1+1,pos2);
	var strYear = dtStr.substring(pos2+1);
	strYr = strYear;

	if (strDay.charAt(0)=="0" && strDay.length>1)
	    strDay = strDay.substring(1);
	if (strMonth.charAt(0)=="0" && strMonth.length>1)
	    strMonth = strMonth.substring(1);

	for (var i = 1; i <= 3; i++) {
		if (strYr.charAt(0)=="0" && strYr.length>1) strYr=strYr.substring(1);
	}

	month = parseInt(strMonth)
	day = parseInt(strDay)
	year = parseInt(strYr)

	if (pos1==-1 || pos2==-1) {
		return false;
	}
	if (strMonth.length<1 || month<1 || month>12) {
		return false;
	}
	if (strDay.length<1 || day<1 || day>31 || (month==2 && day>daysInFebruary(year)) || day > daysInMonth[month]) {
		return false;
	}
	if (strYear.length != 4 || year==0 || year<minYear || year>maxYear) {
		return false;
	}
	if (dtStr.indexOf(dtCh,pos2+1)!=-1 || isInteger(stripCharsInBag(dtStr, dtCh))==false) {
		return false;
	}

    return true;
}