apex:actionSupport is a tag that should be used to display different text while an apex:commandButton is processing an action. apex:actionSupport is a component that can be used to add AJAX support to other components, such as buttons, links, or input fields. apex:actionSupport can specify an action to be executed, an event to trigger the action, and a rerender attribute to update a part of the page. By using apex:actionSupport inside an apex:commandButton, the developer can display different text while the button is processing the action, such as "Processing..." or "Please wait...". For example, the developer can use the following code to display different text while the button is processing the action:
<apex:commandButton value="Submit" action="{!submit}"> <apex:actionSupport event="onclick" rerender="buttonText"/> <apex:facet name="caption"> <apex:outputPanel id="buttonText"> <apex:outputText value="Processing..." rendered="{!processing}"/> <apex:outputText value="Please wait..." rendered="{!NOT(processing)}"/> </apex:outputPanel> </apex:facet> </apex:commandButton>