[Web LA] Fix easing

packages/react-native-reanimated/src/Easing.ts

@@ -313,4 +313,15 @@ const EasingObject = {
   inOut,
 };
 
+export const EasingNameSymbol = Symbol('easingName');
+
+for (const [easingName, easing] of Object.entries(EasingObject)) {
+  Object.defineProperty(easing, EasingNameSymbol, {
+    value: easingName,
+    configurable: false,
+    enumerable: false,
+    writable: false,
+  });
+}
+
 export const Easing = EasingObject;

packages/react-native-reanimated/src/layoutReanimation/web/componentUtils.ts

@@ -21,14 +21,26 @@ import type { ReanimatedSnapshot, ScrollOffsets } from './componentStyle';
 import { setElementPosition, snapshots } from './componentStyle';
 import { Keyframe } from '../animationBuilder';
 import { ReducedMotionManager } from '../../ReducedMotion';
+import { EasingNameSymbol } from '../../Easing';
 
 function getEasingFromConfig(config: CustomConfig): string {
-  const easingName =
-    config.easingV && config.easingV.name in WebEasings
-      ? (config.easingV.name as WebEasingsNames)
-      : 'linear';
+  if (!config.easingV) {
+    return `cubic-bezier(${WebEasings.linear.toString()})`;
+  }
+
+  const easingName = config.easingV[EasingNameSymbol];
+
+  if (!(easingName in WebEasings)) {
+    console.warn(
+      `[Reanimated] Selected easing is not currently supported on web.`
+    );
+
+    return `cubic-bezier(${WebEasings.linear.toString()})`;
+  }
 
-  return `cubic-bezier(${WebEasings[easingName].toString()})`;
+  return `cubic-bezier(${WebEasings[
+    easingName as WebEasingsNames
+  ].toString()})`;
 }
 
 function getRandomDelay(maxDelay = 1000) {

packages/react-native-reanimated/src/layoutReanimation/web/config.ts

@@ -57,8 +57,13 @@ export interface AnimationConfig {
   reversed: boolean;
 }
 
+interface EasingType {
+  (): number;
+  [EasingNameSymbol: symbol]: string;
+}
+
 export interface CustomConfig {
-  easingV?: () => number;
+  easingV?: EasingType;
   durationV?: number;
   delayV?: number;
   randomizeDelay?: boolean;