how to use render and rerender in visualforce page in Salesforce?

Render: – Is used to show/hide the particular block, output panel or input/output fields based on the condition.

Example: – You have 2 fields one is visible and second is hidden, you want the second field to be visible when the first field is filled then use render.

<apex:pageBlockTable value=”{!empList}” var=”emp” rendered=”{!empList.size > 0}”>
<apex:column value=”{!emp.Name}”/>
</apex:pageBlockTable>

reRerender: – Is used to refresh the particular output panel, block, and or fields after a server request has been completed. It uses Id to reRender.

Example: – You have a VF page where you want to add Contacts related to Account and also wanted to show the recently added Contacts then use reRender to refresh the block which is showing the contact list.

renderAs: – Is used to open the Visualforce Page in different format like- HTML, pdf, and excel

Example: – To show the invoice in PDF format.

for pdf – renderAs =”pdf”

for HTML – renderAs =”html”