JAVASCRIPT

Developing a simple validation library in JavaScript: continued

This series of articles mainly lists some of the most commonly used JavaScript functions for client side validation of HTML forms. You can reuse these scripts to inject into server side controls easily.

Author Info:

By: Jagadish Chaterjee

Poor Best

Rating:

/ 7

February 22, 2006

TABLE OF CONTENTS:

<html>
      <head>
            <script id="clientEventHandlersJS" language="javascript">
<!--
functionisValidEmail(val){
    val = val.toLowerCase( );
    if (val.indexOf("@") > 1) {
        var addr = val.substring(0, val.indexOf("@"));
        var domain = val.substring(val.indexOf("@") + 1, val.length);
        // at least one top level domain required
        if (domain.indexOf(".") == -1) {
            return false;
        }
        // parse address portion first, character by character
        for (var i = 0; i < addr.length; i++) {
            oneChar = addr.charAt(i).charCodeAt(0);
            // dot or hyphen not allowed in first position; dot in last
            if ((i == 0 && (oneChar == 45 || oneChar == 46)) ||
                (i == addr.length - 1 && oneChar == 46)) {
                return false;
            }
            // acceptable characters (- . _ 0-9 a-z)
            if (oneChar == 45 || oneChar == 46 || oneChar == 95 ||
                (oneChar > 47 && oneChar < 58) || (oneChar > 96 && oneChar < 123))
{
                continue;
            } else {
                return false;
            }
        }
        for (i = 0; i < domain.length; i++) {
            oneChar = domain.charAt(i).charCodeAt(0);
            if ((i == 0 && (oneChar == 45 || oneChar == 46)) ||
                ((i == domain.length - 1 || i == domain.length - 2) && oneChar == 46))
{
                return false;
            }
            if (oneChar == 45 || oneChar == 46 || oneChar == 95 ||
                (oneChar > 47 && oneChar < 58) || (oneChar > 96 && oneChar < 123))
{
                continue;
            } else {
                return false;
            }
        }
        return true;
    }
    return false;
}

function Button1_onclick() {
var v = document.all("txtEMail").value;
alert(isValidEmail(v));
}
//-->
            </script>
      </head>
      <body>
            <form id="form1">
                  Enter EMail address:<input type="text" id="txtEMail" NAME="txtEMail"> <input type="button" value="Validate" id="Button1"
name="Button1" onclick="return Button1_onclick()">
            </form>
      </body>
</html>

From the above heavy JavaScript, you should now conclude that using “regular expression” (as specified in my previous article) is the best simple method.

Next: Validation for a positive integer (only digits, no symbols) >>