Factor out screen tandem name suffix, see #267

js/PhetioIDUtils.js

@@ -26,6 +26,7 @@
   const VIEW_COMPONENT_NAME = 'view';
   const COLORS_COMPONENT_NAME = 'colors';
   const CONTROLLER_COMPONENT_NAME = 'controller';
+  const SCREEN_COMPONENT_NAME = 'Screen';
 
   /**
    * Helpful methods for manipulating phetioIDs. Used to minimize the amount of duplicated logic specific to the string
@@ -120,9 +121,8 @@
       for ( let i = 0; i < phetioIDParts.length; i++ ) {
         const componentPart = phetioIDParts[ i ];
         screenIDParts.push( componentPart );
-        const screenMarker = 'Screen';
-        const indexOfScreenMarker = componentPart.indexOf( screenMarker );
-        if ( indexOfScreenMarker > 0 && indexOfScreenMarker + screenMarker.length === componentPart.length ) { // endsWith proxy
+        const indexOfScreenMarker = componentPart.indexOf( SCREEN_COMPONENT_NAME );
+        if ( indexOfScreenMarker > 0 && indexOfScreenMarker + SCREEN_COMPONENT_NAME.length === componentPart.length ) { // endsWith proxy
           return screenIDParts.join( SEPARATOR );
         }
       }

js/Tandem.ts

@@ -88,6 +88,8 @@ class Tandem {
   public static OPT_OUT: Tandem;
   public static REQUIRED: Tandem;
 
+  public static readonly SCREEN_TANDEM_NAME_SUFFIX = 'Screen';
+
   /**
    * Typically, sims will create tandems using `tandem.createTandem`.  This constructor is used internally or when
    * a tandem must be created from scratch.
@@ -421,7 +423,7 @@ class RootTandem extends Tandem {
                             name === OPTIONAL_TANDEM_NAME ||
                             name === TEST_TANDEM_NAME ||
                             name === window.phetio.PhetioIDUtils.GENERAL_COMPONENT_NAME ||
-                            _.endsWith( name, 'Screen' );
+                            _.endsWith( name, Tandem.SCREEN_TANDEM_NAME_SUFFIX );
       assert && assert( allowedOnRoot, `tandem name not allowed on root: "${name}"; perhaps try putting it under general or global` );
     }