professional_javascript_for_web/ch14/FormFieldEventsExample01.htm

<!DOCTYPE html>
<html>
<head>
    <title>Form Field Events Example</title>
    <script type="text/javascript" src="EventUtil.js"></script>
</head>
<body>
    <p>The textbox will receive focus as soon as the page loads. You can then start typing.</p>
    <form method="post" action="javascript:alert('Form submitted!')" id="myForm">        
        <div>
            <label for="comments">Type numbers:</label><br />
            <input type="text" id="txtNumbers" name="numbers" />
        </div>
        <input type="submit" value="Submit Form" id="submit-btn" />
    </form>     
    <script type="text/javascript">
        EventUtil.addHandler(window, "load", function(event){
            var textbox = document.forms[0].elements[0];
            
            EventUtil.addHandler(textbox, "focus", function(event){
                event = EventUtil.getEvent(event);
                var target = EventUtil.getTarget(event);
                
                target.style.backgroundColor = "yellow";
            });

            EventUtil.addHandler(textbox, "blur", function(event){
                event = EventUtil.getEvent(event);
                var target = EventUtil.getTarget(event);
                
                if (/[^\d]/.test(target.value)){
                    target.style.backgroundColor = "red";
                } else {
                    target.style.backgroundColor = "";
                }
            });

            EventUtil.addHandler(textbox, "change", function(event){
                event = EventUtil.getEvent(event);
                var target = EventUtil.getTarget(event);
                
                if (/[^\d]/.test(target.value)){
                    target.style.backgroundColor = "red";
                } else {
                    target.style.backgroundColor = "";
                }
            });

            textbox.focus();
        });               

    
    </script>
</body>
</html>