From 7fe3f25791bf2f66152eb7b3465f25fae3b57bd0 Mon Sep 17 00:00:00 2001
From: MichaelWest22 <michael@latent.nz>
Date: Thu, 19 Dec 2024 23:37:03 +1300
Subject: [PATCH] Improve persistentIdSet performance

---
 src/idiomorph.js | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/idiomorph.js b/src/idiomorph.js
index 1c9dd74..385256b 100644
--- a/src/idiomorph.js
+++ b/src/idiomorph.js
@@ -1204,15 +1204,17 @@ var Idiomorph = (function () {
          * @returns {Set<string>} the id set of all persistent nodes that exist in both old and new content
          */
         function persistentIdSet(oldContent, newContent) {
-            let idSet = new Set();
+            let matchIdSet = new Set();
+            let oldIdSet = new Set();
             for (const oldNode of nodesWithIds(oldContent)) {
-                for (const newNode of nodesWithIds(newContent)) {
-                    if (oldNode.id === newNode.id) {
-                        idSet.add(oldNode.id);
-                    }
+                oldIdSet.add(oldNode.id);
+            }
+            for (const newNode of nodesWithIds(newContent)) {
+                if (oldIdSet.has(newNode.id)) {
+                    matchIdSet.add(newNode.id);
                 }
             }
-            return idSet;
+            return matchIdSet;
         }
 
         //=============================================================================