Show or Hide fields in visualforce page using action function

VF:
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<apex:page controller="actionFunctionController" tabStyle="Account">

    <apex:form >

        <apex:actionFunction name="priorityChangedJavaScript" action="{!priorityChanged}" rerender="out"/>

        <apex:pageBlock >

            <apex:pageBlockSection title="If you will select High Customer Priority then phone textbox will be shown" columns="1" id="out" collapsible="false">

                <apex:inputField value="{!acc.CustomerPriority__c}" onchange="priorityChangedJavaScript()"/>

                <apex:inputField value="{!acc.Phone}" rendered="{!showPhone}"/>

            </apex:pageBlockSection>

        </apex:pageBlock>

    </apex:form>

</apex:page>




Apex:

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public class actionFunctionController {

    public Account acc{get;set;}

    public Boolean showPhone{get;set;}

 

    public actionFunctionController(){

        acc = new Account();

        showPhone = false;

    }

 

    public PageReference priorityChanged(){

        if(acc.CustomerPriority__c == 'High'){

            showPhone = true;

        }

        else{

            showPhone = false;

        }

        return null;

    }

}

Screenshot:

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