[JAVA] How to execute action attribute processing only when the confirmation dialog with h: commandButton is OK

--Environment - CentOS Linux release 7.8.2003 (Core) - Eclipse IDE for Enterprise Java Developers.Version: 2020-03 (4.15.0) - openjdk version "11.0.7" 2020-04-14 LTS - JSF 2.3.9

Thing you want to do

1. Press the button to display the confirmation dialog
2. Click the [OK] button in the confirmation dialog to execute the business logic of the action attribute.
3. Nothing happens when the [Cancel] button is pressed in the confirmation dialog.

How to execute the action attribute process only when the confirmation dialog is OK

*. The html tag and next.xhtml are omitted. Use window.confirm for the confirmation dialog.

base.xhtml

<h:head>
  <title>For ponsuke's Qiita</title>
  <script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
  <h:outputScript library="js" name="base.js"/>
</h:head>
<h:body>
<h3>This is screen A</h3>
<h:form id="formId">
  <div>
    <h:commandButton value="Screen transition"
      onclick="return confirmMessage();"
      action="#{sampleBean.showNextPage()}" />
  </div>
</h:form>
</h:body>

base.js

/**
 *Display a confirmation dialog.
 * @return {boolean}Selection result in confirmation dialog true:Press the OK button.
 */
function confirmMessage() {
    return window.confirm('Can I change the screen?');
}

SampleBean.java

package brans;

import javax.faces.view.ViewScoped;
import javax.inject.Named;

@Named
@ViewScoped
public class SampleBean implements Serializable {
    /** serialVersionUID. */
    private static final long serialVersionUID = -6782548672735889274L;
    /**
     *Display the next page.
     * @return Next page.
     */
    public String showNextPage() {
        return "next.xhtml";
    }
}

Failure case: Do not return with onclick attribute

I'm returning in base.js, so it's good, right? I often fail because I think. The action attribute process is executed regardless of the result of the confirmation dialog. I want someone to explain the reason ...

base.xhtml

<!--abridgement-->
    <h:commandButton value="Screen transition"
      onclick="confirmMessage();"
      action="#{sampleBean.showNextPage()}" />
<!--abridgement-->

Writing like this works fine for each button

    <h:commandButton value="Screen transition"
      onclick="return window.confirm('Can I change the screen?');"
      action="#{sampleBean.showNextPage()}" />