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// A utility function that returns true if a string contains only 
// whitespace characters.
function isblank(s) {
    for(var i = 0; i < s.length; i++) {
        var c = s.charAt(i);
        if ((c != ' ') && (c != '\n') && (c != '\t')) return false;
    }
    return true;
}

// This is the function that performs form verification. It is invoked
// from the onsubmit event handler. The handler should return whatever
// value this function returns.
function verify(f) {
    var msg;
    var empty_fields = "";
    var errors = "";

    // Loop through the elements of the form, looking for all 
    // text and textarea elements that don't have an "optional" property
    // defined. Then, check for fields that are empty and make a list of them.
    // Also, if any of these elements have a "min" or a "max" property defined,
    // verify that they are numbers and in the right range.
    // If the element has a "numeric" property defined, verify that
    // it is a number, but don't check its range.
    // Put together error messages for fields that are wrong.
    for(var i = 0; i < f.length; i++) {
        var e = f.elements[i];
        if (((e.type == "text") || (e.type == "textarea")) && !e.optional) {
            // first check if the field is empty
            if ((e.value == null) || (e.value == "") || isblank(e.value)) {
                empty_fields += "\n          " + e.name;
                continue;
            }

            // Now check for fields that are supposed to be numeric.
            if (e.numeric || (e.min != null) || (e.max != null)) { 
                var v = parseFloat(e.value);
                if (isNaN(v) || 
                    ((e.min != null) && (v < e.min)) || 
                    ((e.max != null) && (v > e.max))) {
                    errors += "- The field " + e.name + " must be a number";
                    if (e.min != null) 
                        errors += " that is greater than " + e.min;
                    if (e.max != null && e.min != null) 
                        errors += " and less than " + e.max;
                    else if (e.max != null)
                        errors += " that is less than " + e.max;
                    errors += ".\n";
                }
            } // end numeric check
			
			// check for emails field
			if (e.email && !isblank(e.value))
			{
				var seenAt = false;
				var append = "";
				for(var j = 0; j < e.value.length; j++)
				{
					var c = e.value.charAt(j);
					if ((c == ' ') || (c == '\n') || (c == '\t'))
					append += "\n           - not contain white space";
					if ((c =='@') && (seenAt == true))
					append += "\n           - contain only one @";
					if ((c =='@'))
					seenAt = true;
				}
				if (seenAt == false)
				append += "\n              - contain exactly one @";
				if (append)
					errors += "- The field " + e.name + " must: " + append;
			} // end email check
			
			// link checker here - ie must be of form http://
			if (e.link && !isblank(e.value))
			{
				var seenAt = false;
				var append = "";

				for(var j = 0; j < e.value.length; j++)
				{
					var c = e.value.charAt(j);
					if ((c == ' ') || (c == '\n') || (c == '\t')) // must have no spaces
					append += "\n           - not contain white space";
				}
				// must have http:// in it
				if (append)
					errors += "- The field " + e.name + " must: " + append;
			} // end if link
        }
    }

    // Now, if there were any errors, display the messages, and
    // return false to prevent the form from being submitted. 
    // Otherwise return true.
    if (!empty_fields && !errors) return true;

    msg  = "______________________________________________________\n\n"
    msg += "The form was not submitted because of the following error(s).\n";
    msg += "Please correct these error(s) and re-submit.\n";
    msg += "______________________________________________________\n\n"

    if (empty_fields) {
        msg += "- The following required field(s) are empty:" 
                + empty_fields + "\n";
        if (errors) msg += "\n";
    }
    msg += errors;
    alert(msg);
    return false;
}

//-->