Adding and Removing Options from Select box

4 April 2009

Adding options to a select element in html using dynamic javascript

function addOption(selectbox, value, text){
    var optn = new Option();
    optn.text = text;
    optn.value = value;
    selectbox.options.add(optn);
}

We can add new options to a select element using the options array present in the select object. We can create a new option using the new operator and Option class provided by javascript or by using document.createElement(“OPTION”);

Removing all options from a select box

function removeAllOptions(selectbox){
    if(selectbox && selectbox.options && selectbox.options.length > 0){
        while(selectbox.options.length > 0){
            selectbox.remove(0);
        }
    }
}

To remove a option from select element we can use the remove method in the select object. It takes the index of the option to be removed as an argument.

 

Here is a sample html snippet which uses select element and addition and removal of options using javascript

<html>  
    <body>
        Select Box 1: <select id=”selectbox1″></select>
        <br />
        <input type=”button” onclick=”clearSelectBox(‘selectbox1′)” value=”Remove” />
        <input type=”button” onclick=”addItems(‘selectbox1′)” value=”Add” />
    </body>

    <script>
        function removeAllOptions(selectbox){
            if(selectbox && selectbox.options && selectbox.options.length > 0){
                while(selectbox.options.length > 0){
                    selectbox.remove(0);
                }
            }
        }

        function addOption(selectbox, value, text){
            var optn = new Option();
            optn.text = text;
            optn.value = value;
            selectbox.options.add(optn);
        }

        function clearSelectBox(selectBoxId){
            var selectbox = document.getElementById(selectBoxId);
            removeAllOptions(selectbox);
        }

        function addItems(selectBoxId){
            var selectbox = document.getElementById(selectBoxId);
            addOption(selectbox, 1, ‘One’);
            addOption(selectbox, 2, ‘Two’);
            addOption(selectbox, 3, ‘Three’);
            addOption(selectbox, 4, ‘Four’);
            addOption(selectbox, 5, ‘Five’);
            addOption(selectbox, 6, ‘Six’);
        }

        window.onload = addItems(‘selectbox1′)
    </script>
</html>

Enable GC dumb in JVM

12 March 2009

-verbose:gc — prints basic information about GC to the standard output
-XX:+PrintGCTimeStamps — prints the times that GC executes
-XX:+PrintGCDetails — prints statistics about different regions of memory in the JVM
-Xloggc:<file> — logs the results of GC in the given file

Enable Jconsole In Tomcat

12 March 2009

Add the following properties to JVM settings

-Dcom.sun.management.jmxremote.ssl=false
-Dcom.sun.management.jmxremote.authenticate=false
-Dcom.sun.management.jmxremote.port=<port_number>
-Dcom.sun.management.jmxremote

<port_number> can be anything like 5000

Retaining scroll position after store load

23 February 2009

view config:
onLoad: Ext.emptyFn,
listeners: {
beforerefresh: function(v) {
v.scrollTop = v.scroller.dom.scrollTop;
},
refresh: function(v) {
v.scroller.dom.scrollTop = v.scrollTop;
},

}


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