game: Add support for a static "meta" field to hold game metadata

We use a static getter/setter function for this since JavaScript
doesn't yet have wide support for static fields.

Also, we duplicate the data on both a field within the class itself
(Game._meta) as well as in the prototype (Game.prototype). The purpose
of this is so that we can access this meta-data as either a class
static (Game.meta) or via an instance (some_game.meta).

diff --git a/game.js b/game.js
index 20cd2411e2275ff8aef51e1c35a3772931815b6b..5bbd7f503885a964105a90266f5e36d8cd981210 100644 (file)
--- a/game.js
+++ b/game.js
@@ -6,6 +6,26 @@ class Game {
     this.next_client_id = 1;
   }
 
+  /* Suport for game meta-data.
+   *
+   * What we want here is an effectively static field that is
+   * accessible through either the class name (SomeGame.meta) or an
+   * instance (some_game.meta). To pull this off we do keep two copies
+   * of the data. But the game classes can just set SomeGame.meta once
+   * and then reference it either way.
+   */
+  static set meta(data) {
+    /* This allows class access (SomeGame.meta) via the get method below. */
+    this._meta = data;
+
+    /* While this allows access via an instance (some_game.meta). */
+    this.prototype.meta = data;
+  }
+
+  static get meta() {
+    return this._meta;
+  }
+
   add_client(response) {
     const id = this.next_client_id;
     this.clients.push({id: id,