popup when a picklist is selected

Question

I am trying to show a popup when picklist is selected but I am unable to do I tired this https://developer.salesforce.com/forums/?id=906F0000000DDKiIAO dint work :(

    <apex:outputPanel">
      <apex:outputLabel>Pick one</apex:outputLabel><br/>
      <apex:selectList id="picklst" value="{!selectedValue}" size="1" required="TRUE" multiselect="FALSE">
          <apex:selectOptions value="{!Lst}"/>
          <apex:actionSupport event="onchange" action="{!func}"/>
      </apex:selectList>
    </apex:outputPanel>

I mean it works but doesn't execute

   <apex:actionSupport event="onchange" action="{!func}"/> 

as this render the VF components to display form page. I want to display a popup when someone change to value1 to value2. saying data will be lost. Any ideas

Answer 1

You need to make changes in your Actionsupport to make it work. As you want to call JavaScript so instead of action use onsubmit. Set rerender to none to stop the page reload.

<apex:actionSupport event="onchange" onsubmit="alert('You will lost value');" rerender="none"/>

But in your use case you don't need actionsupport as apex:selectList also support onchange event. You can simplyuse that as well.

<apex:selectList id="picklst" value="{!selectedValue}" size="1" required="true" multiselect="false" onchange="alert('You will lost value');">