.: How to Retrieve Environment Variable Current Value in JavaScript for Dynamics 365

In Dynamics 365, Environment Variables let you externalize configurable values such as URLs, keys, or feature toggles without changing the solution code.

Each variable can have:

A Default Value (defined during solution development)
A Current Value (set per environment during deployment)

When working with JavaScript, especially on forms or PCF controls, you may need to retrieve the effective value of an environment variable—preferably the Current Value if available, falling back to Default Value.

✅ Recommended Approach: Use FetchXML with `link-entity`

Since the Web API OData endpoint for environmentvariabledefinition does not expose environmentvariablevalue as a navigation property, we use FetchXML to join the two tables in one call.

✅ Sample Function

/**
 * Retrieves the effective value of an environment variable using FetchXML.
 * Prioritizes the override "Current Value" from environmentvariablevalue, falls back to "Default Value".
 * 
 * @param {string} varName - The schema name of the environment variable.
 * @param {function(string):void} successCallback - Called with the resolved value.
 * @param {function(string):void} errorCallback - Called with an error message if any error occurs.
 */
function comm_GetEnvironmentVariableValue(varName, successCallback, errorCallback)
{
    var fetchXml =
        "<fetch top='1'>" +
        "  <entity name='environmentvariabledefinition'>" +
        "    <attribute name='environmentvariabledefinitionid'/>" +
        "    <attribute name='defaultvalue'/>" +
        "    <filter>" +
        "      <condition attribute='schemaname' operator='eq' value='" + varName + "'/>" +
        "    </filter>" +
        "    <link-entity name='environmentvariablevalue' from='environmentvariabledefinitionid' to='environmentvariabledefinitionid' link-type='outer'>" +
        "      <attribute name='value'/>" +
        "    </link-entity>" +
        "  </entity>" +
        "</fetch>";

    var encodedUrl = "?fetchXml=" + encodeURIComponent(fetchXml);

    Xrm.WebApi.retrieveMultipleRecords("environmentvariabledefinition", encodedUrl).then(
        function(result)
        {
            if (result.entities.length > 0)
            {
                var record = result.entities[0];
                var defaultVal = record["defaultvalue"];
                
                // Find override value (alias from link-entity)
                var overrideKey = Object.keys(record).find(k => k.endsWith(".value"));
                var overrideVal = overrideKey ? record[overrideKey] : null;
                
                var effectiveVal = overrideVal || defaultVal;
                successCallback(effectiveVal);
            }
            else
            {
                errorCallback("Environment variable '" + varName + "' not found.");
            }
        },
        function(error)
        {
            errorCallback("Error retrieving environment variable: " + error.message);
        }
    );
}

🧪 How to Debug from Browser Console

You can quickly test this function by running the following debug version in your browser console (inside a Dynamics 365 form):

function debug_GetEnvVarValue_FetchXML()
{
    var varName = "hx_CreateDocumentLocationFlowUrl"; // Replace with your variable's schema name

    comm_GetEnvironmentVariableValue(varName,
        function(val)
        {
            console.log(varName + ":", val);
        },
        function(err)
        {
            console.error("Error:", err);
        }
    );
}

📝 Notes

This approach does not require two API calls, making it efficient and cleaner.
FetchXML link-entity uses link-type='outer' to gracefully handle cases where no override exists.
Works for all simple types (Text, Number, JSON, etc.).

📌 Summary

To reliably retrieve the current value of an environment variable in client-side code:

Use a fetchXml query that links environmentvariabledefinition and environmentvariablevalue.
Look for .value keys in the returned result.
Fall back to defaultvalue if no override is present.

This method is tested and safe for use in production Dynamics 365 environments.

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