look up order in a map

main.js

@@ -73,13 +73,12 @@ module.exports = class RibbonClasp extends Plugin {
       return;
     }
 
+    // anything we haven't seen before sorts to the bottom, in the order it came in
+    const rank = new Map(order.map((id, i) => [id, i]));
     const sorted = [...ribbon.items].sort((a, b) => {
-      const ia = order.indexOf(a.id);
-      const ib = order.indexOf(b.id);
-      if (ia === -1 && ib === -1) return 0;
-      if (ia === -1) return 1;
-      if (ib === -1) return -1;
-      return ia - ib;
+      const ia = rank.get(a.id) ?? Infinity;
+      const ib = rank.get(b.id) ?? Infinity;
+      return ia === ib ? 0 : ia - ib;
     });
 
     const changed = sorted.some((item, i) => ribbon.items[i] !== item);