From f7861bd75e9a21e1ad02b065610771b030551b1c Mon Sep 17 00:00:00 2001
From: Ermad <me@ermad.xyz>
Date: Mon, 23 Feb 2026 11:31:13 -0500
Subject: [PATCH 1/2] Added an option to set storage engine per store, #63

---
 index.d.ts |  1 +
 index.js   | 24 +++++++++++++-----------
 2 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/index.d.ts b/index.d.ts
index 0aaae47..bdac514 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -57,6 +57,7 @@ interface PersistentSimpleOptions {
    * Does not synchronize changes from other browser tabs
    */
   listen?: boolean
+  storage?: PersistentStore
 }
 
 export type PersistentOptions =
diff --git a/index.js b/index.js
index 3e00aa5..6477fbb 100644
--- a/index.js
+++ b/index.js
@@ -38,20 +38,21 @@ export function setPersistentEngine(storage, events) {
 }
 
 export function persistentAtom(name, initial = undefined, opts = {}) {
+  let storage = opts.storage || storageEngine
   let encode = opts.encode || identity
   let decode = opts.decode || identity
 
-  let prevValue = storageEngine[name]
-  let store = atom(name in storageEngine ? decode(prevValue) : initial)
+  let prevValue = storage[name]
+  let store = atom(name in storage ? decode(prevValue) : initial)
 
   let set = store.set
   store.set = newValue => {
     prevValue = encode(newValue)
 
     if (typeof prevValue === 'undefined') {
-      delete storageEngine[name]
+      delete storage[name]
     } else {
-      storageEngine[name] = prevValue
+      storage[name] = prevValue
     }
 
     set(newValue)
@@ -64,14 +65,14 @@ export function persistentAtom(name, initial = undefined, opts = {}) {
       } else {
         set(decode(e.newValue))
       }
-    } else if (!storageEngine[name]) {
+    } else if (!storage[name]) {
       set(initial)
     }
   }
 
   function restore() {
-    if (prevValue === storageEngine[name]) return
-    store.set(name in storageEngine ? decode(storageEngine[name]) : initial)
+    if (prevValue === storage[name]) return
+    store.set(name in storage ? decode(storage[name]) : initial)
   }
 
   onMount(store, () => {
@@ -114,6 +115,7 @@ export function persistentJSON(key, initial = null, opts = {}) {
 }
 
 export function persistentMap(prefix, initial = {}, opts = {}) {
+  let storage = opts.storage || storageEngine
   let encode = opts.encode || identity
   let decode = opts.decode || identity
 
@@ -125,7 +127,7 @@ export function persistentMap(prefix, initial = {}, opts = {}) {
       if (opts.listen !== false && eventsEngine.perKey) {
         eventsEngine.removeEventListener(prefix + key, listener, restore)
       }
-      delete storageEngine[prefix + key]
+      delete storage[prefix + key]
     } else {
       if (
         opts.listen !== false &&
@@ -134,7 +136,7 @@ export function persistentMap(prefix, initial = {}, opts = {}) {
       ) {
         eventsEngine.addEventListener(prefix + key, listener, restore)
       }
-      storageEngine[prefix + key] = encode(newValue)
+      storage[prefix + key] = encode(newValue)
     }
   }
 
@@ -170,9 +172,9 @@ export function persistentMap(prefix, initial = {}, opts = {}) {
 
   function restore() {
     let data = { ...initial }
-    for (let key in storageEngine) {
+    for (let key in storage) {
       if (key.startsWith(prefix)) {
-        data[key.slice(prefix.length)] = decode(storageEngine[key])
+        data[key.slice(prefix.length)] = decode(storage[key])
       }
     }
     for (let key in data) {

From 93482d5c5ad8e46e8961444158d3b1255c68952f Mon Sep 17 00:00:00 2001
From: Ermad <me@ermad.xyz>
Date: Mon, 23 Feb 2026 14:40:42 -0500
Subject: [PATCH 2/2] Adjusted size limit for storage option change

Adjusted persistentMap test to set storage option before initilization
---
 package.json     | 2 +-
 test/map.test.ts | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/package.json b/package.json
index ff09056..327624f 100644
--- a/package.json
+++ b/package.json
@@ -75,7 +75,7 @@
       "import": {
         "./index.js": "{ persistentAtom }"
       },
-      "limit": "296 B"
+      "limit": "308 B"
     },
     {
       "name": "Map",
diff --git a/test/map.test.ts b/test/map.test.ts
index 1e23b2f..69e384e 100644
--- a/test/map.test.ts
+++ b/test/map.test.ts
@@ -153,10 +153,10 @@ describe('persistentMap', () => {
   })
 
   test('has test API', async () => {
+    useTestStorageEngine()
     let settings = persistentMap<{ lang: string }>('settings:', {
       lang: 'en'
     })
-    useTestStorageEngine()
 
     let events: string[] = []
     let unbind = settings.listen(value => {