Visualforce Developer Guide

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Introducing Visualforce
Tools for Visualforce Development
Getting a Quick Start with Visualforce
Customizing the Appearance and Output of Visualforce Pages
Standard Controllers
Standard List Controllers
Custom Controllers and Controller Extensions
Advanced Examples
Override Buttons, Links, and Tabs with Visualforce
Using Static Resources
Creating and Using Custom Components
Dynamic Visualforce Bindings
Dynamic Visualforce Components
Integrate Email with Visualforce
Visualforce Charting
Creating Maps with Visualforce
Render Flows with Visualforce
Templating with Visualforce
Developing Salesforce Apps with Visualforce
Adding Visualforce to a Salesforce AppExchange App
Using JavaScript in Visualforce Pages
Communicating Across the DOM with Lightning Message Service
Create a Message Channel
Publish on a Message Channel
Subscribe and Unsubscribe from a Message Channel
Considerations and Limitations
Visualforce Best Practices
Standard Visualforce Component Reference
Appendices
PDF

Communicating Across the DOM with Lightning Message Service

Use Lightning message service to communicate across the DOM within a Lightning page. Communicate between Visualforce pages embedded in the same Lightning page, Aura components, and Lightning web components, including components in a utility bar and pop-out utilities. Choose whether a component subscribes to messages from the entire application, or from only the active area.

If you're switching from Salesforce Classic to Lightning Experience, you can now build Lightning web components that can communicate with existing Visualforce pages or Aura components. You can also use Lightning message service to communicate with softphones via Open CTI.

Lightning message service is available in Lightning Experience and as a beta feature for Lightning components used in Experience Builder sites.

Important

To access Lightning message service in Visualforce, use the $MessageChannel global variable. A message is a serializable JSON object. Examples of data that you can pass in a message include strings, numbers, objects, and booleans. A message can’t contain functions and symbols. The $MessageChannel global variable is only available in Lightning Experience.

Use Message Channels Created Within Your Org

Here's an example of using a Lightning message channel developed within your org.

<apex:page>
    <script>
        // Load the MessageChannel token in a variable
        var SAMPLEMC = "{!$MessageChannel.SampleMessageChannel__c}";
    </script>
</apex:page>

Here, we reference a custom message channel with a formula expression {!$MessageChannel.SampleMessageChannel__c}. This expression creates a token that we assign to the variable SAMPLEMC. This token is unique to your custom message channel and can be used within the Lightning message service API methods. The syntax SampleMessageChannel__c refers to a custom instance of the LightningMessageChannel metadata type. The __c suffix indicates that it’s custom, but note that it isn’t a custom object. See Create a Message Channel to learn more.

If your org has a namespace, don’t include it in your message channel expression. For example, if your org’s namespace is MyNamespace, the message channel expression remains "{!$MessageChannel.SampleMessageChannel__c}".

Use Message Channels Created Outside Your Org

To use message channels from packages created by developers outside of your org, reference them with the syntax {!$MessageChannel.Namespace_name__c}. For example, if SampleMessageChannel wasn’t local to your org and came from a package with the namespace SamplePackageNamespace, the syntax would be {$MessageChannel.SamplePackageNamespace__SampleMessageChannel__c}.