function isDigit(num) {
    if (num.length>1){
	return false;
    }
    var string="1234567890";
    if (string.indexOf(num)!=-1){
	return true;
    }
    return false;
}




function trimToMailAddress(s){
    var res = "";
    var i = 0;
    for(i = 0; s != null && i < s.length; i++){
	if(isDigit(s.charAt(i))||isLetter(s.charAt(i))||s.charAt(i)=='@'||s.charAt(i)=='.'){
            res += s.charAt(i);
	}
    }

    return res;
}


function leaveLettersAndBlanks(s){
    var res = "";
    var i = 0;
    for(i = 0; s != null && i < s.length>0;i++){
        res = (isLetter(s.charAt(i)))||s.charAt(i)==' '?res+s.charAt(i):res;
    }
    return res;
}



function leaveNumbersAndBlanks(s){
    var res = "";
    var i = 0;
    for(i = 0; s != null && i < s.length>0;i++){
        res = (isDigit(s.charAt(i)))||s.charAt(i)==' '?res+s.charAt(i):res;
    }
    return res;
}



function isLetter (c){
    return ( ((c >= "a") && (c <= "z")) || ((c >= "A") && (c <= "Z")) );
}