Replacing the non-primary material on a multi-material object

I need to replace the non-primary material on a multi-material object. The replace material puzzle will only replace the first material in an object. I think that I have a reasonable solution, but I would like someone with more v3d API experience to critique my code. Here is the solution that I put together

function prepareExternalInterface(app) {

    app.ExternalInterface.replaceMaterialByName = function (oldMatName, newMatName, objName) {
        v3d.apps[0].scene.getObjectByName(objName).traverse(child => {
            if (child.material) {
                console.log(child.material.name);
                if (child.material.name === oldMatName) {
                    console.log("replacing " + oldMatName + " with " + newMatName + " on " + child.name);
                    child.material = v3d.SceneUtils.getMaterialsByName(v3d.apps[0], newMatName)[0];
                }
            }
        });
    }
    
}

Is there a better way to do this? Also, I did not .clone() the new material before applying it to the target object. In some of the three.js examples that I found, the authors would clone the material before assigning the clone to the object. Is this necessary?

This code is in my prepareExternalInterface(). I am using “v3d.apps[0]” to obtain a reference to the current 3d app. This assumes that there is only one 3d app on the page (which might not be true). Is there a more robust way to obtain the handle of the current 3d app?
Thanks!