professional_javascript_for_web/ch14/SelectboxExample03.htm

<!DOCTYPE html>
<html>
<head>
    <title>Selectbox Example</title>
    <script type="text/javascript" src="EventUtil.js"></script>
</head>
<body>
    
    <form method="post" action="javascript:alert('Form submitted!')" id="myForm">            
        <div>
            <label for="selLocation">Where do you want to live?</label>
            <select name="location" id="selLocation" size="5" multiple>
                <option value="Sunnyvale, CA">Sunnyvale</option>
                <option value="Los Angeles, CA">Los Angeles</option>
                <option value="Mountain View, CA">Mountain View</option>
                <option value="">China</option>
                <option>Australia</option>
            </select>
        </div>
        <div>
            <input type="button" value="Select first option" id="btnFirst">
            <input type="button" value="Select second option" id="btnSecond">
            <input type="button" value="Get selected options" id="btnSelected">
        </div>
    </form>     
    <script type="text/javascript">
        (function(){

            function getSelectedOptions(selectbox){
                var result = new Array();
                var option = null;
                
                for (var i=0, len=selectbox.options.length; i < len; i++){
                    option = selectbox.options[i];
                    if (option.selected){
                        result.push(option);
                    }
                }
                
                return result;            
            }

            var btn1 = document.getElementById("btnFirst");
            var btn2 = document.getElementById("btnSecond");
            var btn3 = document.getElementById("btnSelected");
            var selectbox = document.getElementById("selLocation");

            EventUtil.addHandler(btn1, "click", function(event){
                selectbox.options[0].selected = true;
            });
            EventUtil.addHandler(btn2, "click", function(event){
                selectbox.options[1].selected = true;
            });
            EventUtil.addHandler(btn3, "click", function(event){
                var selectedOptions = getSelectedOptions(selectbox);
                var message = "";
                
                for (var i=0, len=selectedOptions.length; i < len; i++){
                    message += "Selected index: " + selectedOptions[i].index + "\nSelected text: " + selectedOptions[i].text + "\nSelected value: " + selectedOptions[i].value + "\n\n";
                }
                
                alert(message);
                
            });
            
        })();
    
    </script>
</body>
</html>