Use fast-deep-equal

package.json

@@ -31,5 +31,8 @@
     "@niivue/niivue": "^0.39.0",
     "react": "^17 || ^18",
     "typescript": "^5.0.0"
+  },
+  "dependencies": {
+    "fast-deep-equal": "^3.1.3"
   }
 }

src/diff.ts

@@ -1,4 +1,5 @@
-import { HasUrlObject } from "./model.ts";
+import { HasUrlObject } from "./model";
+import equal from "fast-deep-equal/es6";
 
 /**
  * A special value which indicates that the difference between two objects is Irreconcilable.
@@ -186,30 +187,14 @@ function diffPrimitive<T extends { [key: string]: any }>(
   const yKeys = Object.keys(y);
   const deletedKeys = setDifference(xKeys, yKeys);
   const addedKeys = setDifference(yKeys, xKeys);
-  const changedKeys = xKeys.filter((key) => !deepishEqual(x[key], y[key]));
+  const changedKeys = xKeys.filter((key) => !equal(x[key], y[key]));
   const diffKeys = addedKeys.concat(changedKeys);
   return {
     ...Object.fromEntries(deletedKeys.map((key) => [key, undefined])),
     ...Object.fromEntries(diffKeys.map((key) => [key, y[key]])),
   };
 }
 
-/**
- * Equality for arrays and primitives.
- */
-function deepishEqual<T>(x: T, y: T): boolean {
-  if (Array.isArray(x)) {
-    if (!Array.isArray(y)) {
-      return false;
-    }
-    return zipArrays(x, y).reduce(
-      (same, [a, b]) => same && deepishEqual(a, b),
-      true,
-    );
-  }
-  return x === y;
-}
-
 function zipArrays<X, Y>(x: X[], y: Y[]): [X, Y][] {
   return x.map((v, i) => [v, y[i]]);
 }