From 1256e1c6aa1bddee2e897ed93d7d3551505ef008 Mon Sep 17 00:00:00 2001
From: Mitchell Hamilton <mitchell@hamil.town>
Date: Thu, 1 Apr 2021 05:21:59 +1000
Subject: [PATCH] Memoize Node.isNodeList and Editor.isEditor (#4072)

* Memoize Node.isNodeList

* Memoize Editor.isEditor
---
 packages/slate/src/interfaces/editor.ts | 13 ++++++++++---
 packages/slate/src/interfaces/node.ts   | 13 ++++++++++++-
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/packages/slate/src/interfaces/editor.ts b/packages/slate/src/interfaces/editor.ts
index 8b03bd7c9..5cc811c35 100755
--- a/packages/slate/src/interfaces/editor.ts
+++ b/packages/slate/src/interfaces/editor.ts
@@ -272,6 +272,8 @@ export interface EditorInterface {
   withoutNormalizing: (editor: Editor, fn: () => void) => void
 }
 
+const IS_EDITOR_CACHE = new WeakMap<object, boolean>()
+
 export const Editor: EditorInterface = {
   /**
    * Get the ancestor above a location in the document.
@@ -549,8 +551,12 @@ export const Editor: EditorInterface = {
    */
 
   isEditor(value: any): value is Editor {
-    return (
-      isPlainObject(value) &&
+    if (!isPlainObject(value)) return false
+    const cachedIsEditor = IS_EDITOR_CACHE.get(value)
+    if (cachedIsEditor !== undefined) {
+      return cachedIsEditor
+    }
+    const isEditor =
       typeof value.addMark === 'function' &&
       typeof value.apply === 'function' &&
       typeof value.deleteBackward === 'function' &&
@@ -569,7 +575,8 @@ export const Editor: EditorInterface = {
       (value.selection === null || Range.isRange(value.selection)) &&
       Node.isNodeList(value.children) &&
       Operation.isOperationList(value.operations)
-    )
+    IS_EDITOR_CACHE.set(value, isEditor)
+    return isEditor
   },
 
   /**
diff --git a/packages/slate/src/interfaces/node.ts b/packages/slate/src/interfaces/node.ts
index 4e8b25e9c..e12a3a764 100755
--- a/packages/slate/src/interfaces/node.ts
+++ b/packages/slate/src/interfaces/node.ts
@@ -86,6 +86,8 @@ export interface NodeInterface {
   ) => Generator<NodeEntry<Text>, void, undefined>
 }
 
+const IS_NODE_LIST_CACHE = new WeakMap<any[], boolean>()
+
 export const Node: NodeInterface = {
   /**
    * Get the node at a specific path, asserting that it's an ancestor node.
@@ -384,7 +386,16 @@ export const Node: NodeInterface = {
    */
 
   isNodeList(value: any): value is Node[] {
-    return Array.isArray(value) && value.every(val => Node.isNode(val))
+    if (!Array.isArray(value)) {
+      return false
+    }
+    const cachedResult = IS_NODE_LIST_CACHE.get(value)
+    if (cachedResult !== undefined) {
+      return cachedResult
+    }
+    const isNodeList = value.every(val => Node.isNode(val))
+    IS_NODE_LIST_CACHE.set(value, isNodeList)
+    return isNodeList
   },
 
   /**