perf: optimize hash function and cache JSON.stringify result

- Rename hashObject to hashString for clarity
- Cache JSON.stringify(value) to avoid duplicate calls
- Add comment about JSON.stringify key order behavior

Author: YasserGomma

src/cookies.ts

@@ -8,13 +8,12 @@ import { InvalidCookieSignature } from './error'
 import type { Context } from './context'
 import type { Prettify } from './types'
 
-// FNV-1a hash for fast object comparison
-const hashObject = (obj: unknown): number => {
+// FNV-1a hash for fast string hashing
+const hashString = (str: string): number => {
 	const FNV_OFFSET_BASIS = 2166136261
 	const FNV_PRIME = 16777619
 
 	let hash = FNV_OFFSET_BASIS
-	const str = JSON.stringify(obj)
 	const len = str.length
 
 	for (let i = 0; i < len; i++) {
@@ -182,22 +181,26 @@ export class Cookie<T> implements ElysiaCookie {
 		if (current === value) return
 
 		// For objects, use hash-based comparison for performance
+		// Note: Uses JSON.stringify for comparison, so key order matters
+		// { a: 1, b: 2 } and { b: 2, a: 1 } are treated as different values
 		if (
 			typeof current === 'object' &&
 			current !== null &&
 			typeof value === 'object' &&
 			value !== null
 		) {
 			try {
-				const newHash = hashObject(value)
+				// Cache stringified value to avoid duplicate stringify calls
+				const valueStr = JSON.stringify(value)
+				const newHash = hashString(valueStr)
 
 				// If hash differs from cached hash, value definitely changed
 				if (this.valueHash !== undefined && this.valueHash !== newHash) {
 					this.valueHash = newHash
 				}
 				// First set (valueHash undefined) OR hashes match: do deep comparison
 				else {
-					if (JSON.stringify(current) === JSON.stringify(value)) {
+					if (JSON.stringify(current) === valueStr) {
 						this.valueHash = newHash
 						return // Values are identical, skip update
 					}