You can actually accomplish this without JavaScript, using only JSF's rendered
attribute, by enclosing the elements to be shown/hidden in a component that can itself be re-rendered, such as a panelGroup, at least in JSF2. For example, the following JSF code shows or hides one or both of two dropdown lists depending on the value of a third. An AJAX event is used to update the display:
<h:selectOneMenu value="#{workflowProcEditBean.performedBy}">
<f:selectItem itemValue="O" itemLabel="Originator" />
<f:selectItem itemValue="R" itemLabel="Role" />
<f:selectItem itemValue="E" itemLabel="Employee" />
<f:ajax event="change" execute="@this" render="perfbyselection" />
</h:selectOneMenu>
<h:panelGroup id="perfbyselection">
<h:selectOneMenu id="performedbyroleid" value="#{workflowProcEditBean.performedByRoleID}"
rendered="#{workflowProcEditBean.performedBy eq 'R'}">
<f:selectItem itemLabel="- Choose One -" itemValue="" />
<f:selectItems value="#{workflowProcEditBean.roles}" />
</h:selectOneMenu>
<h:selectOneMenu id="performedbyempid" value="#{workflowProcEditBean.performedByEmpID}"
rendered="#{workflowProcEditBean.performedBy eq 'E'}">
<f:selectItem itemLabel="- Choose One -" itemValue="" />
<f:selectItems value="#{workflowProcEditBean.employees}" />
</h:selectOneMenu>
</h:panelGroup>
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