function isEmail(string) {

	var intIndexOfAt = string.indexOf("@");

	if (intIndexOfAt > 0) { // if there is something preceeding the at sign

		// indexOf(searchValue[, fromIndex])

		// fromIndex - The location within the calling string to start the search from. 

		// It can be any integer between 0 and the length of the string. The default value is 0.

		var intIndexOfDot = string.indexOf(".",intIndexOfAt);

		if ((intIndexOfDot > intIndexOfAt + 1) && (string.length > intIndexOfDot + 1)) {

		// if there is something between the @ sign and the . sign and

		// if there is something after the . sign

			return true;

		} else {

			return false;

		}

	} else {

		return false;

	}

}



function isValidCharacter(character) {

	var validCharacters=" !@#$%^&*()-_=+`~{}[]|:;<>,./?ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

	if (validCharacters.indexOf(character) != -1) {

		return true;

	} else {

		return false;

	}

}	



function isDigit(character) {

	var validDigits="1234567890";

	// indexOf returns the index within the calling String object of the first 

	// occurrence of the specified value or -1 if the value is not found.

	if (validDigits.indexOf(character) != -1) {

		return true;

	} else {

		return false;

	}

}



function isText(string) {

	for (var i=0; i<string.length; i++) {

		if (!isValidCharacter(string.charAt(i))) {

			return false;

		}

	}

	return true;

}



function isInteger(string) {

	for (var i=0; i<string.length; i++) {

		if (!isDigit(string.charAt(i))) {

			return false; 

		}

	}

	return true;

}



function isNumeric(string) {

	var decimalPoint = false;

	for (var i=0; i<string.length; i++) {

		if (!isDigit(string.charAt(i))) {

			if (string.charAt(i) == ".") {

				if (decimalPoint == true) { 

					return false; 

				} else { 

					decimalPoint = true; 

				}

			} else {

				return false; 

			}

		}

	}

	return true;

}



function isDate(string) { //checks for valid dates

	var dateComponentArray = string.split("/");

	if (dateComponentArray.length == 3) {

		if (!(isInteger(dateComponentArray[0]) && isInteger(dateComponentArray[1]) && isInteger(dateComponentArray[2]))) {

			return false;

		}

		var month = parseInt(dateComponentArray[0]);

		var day = parseInt(dateComponentArray[1]);

		var year = parseInt(dateComponentArray[2]);

		if (dateComponentArray[2].length != 4) {

			return false;

		}

		if (month < 1 || month > 12) {

			return false;

		}

		if (day < 1 || day > 31) {

			return false;

		}

		if ((month==4 || month==6 || month==9 || month==11) && day==31) {

			return false

		}

		if (month == 2) {

			var isleap = (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0));

			if (day>29 || (day==29 && !isleap)) {

				return false;

   			}

		}

		return true;

	}

}



function trim(string) { //removes trailing and leading spaces of a string

	while(string.charAt(0) == " ") {

		string = string.substring(1, string.length);

	}

	while(string.charAt(string.length - 1) == " ") {

		string = string.substring(0, string.length - 1);

	}

	return(string);

}



function len(string) { //returns the length of a string

	return(string.length);

}