From bb3093181de641bd8abbff0a2dd86bdba399cccc Mon Sep 17 00:00:00 2001
From: Justin Edelson <jedelson@pagerduty.com>
Date: Tue, 20 Jun 2023 15:47:21 -0400
Subject: [PATCH] support custom serialization/deserialization. fixes #75

---
 README.md    | 20 ++++++++++++++++++++
 src/index.ts | 14 ++++++++++----
 2 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 126d77a..e952109 100644
--- a/README.md
+++ b/README.md
@@ -108,6 +108,10 @@ import { recoilPersist } from 'recoil-persist'
 const { persistAtom } = recoilPersist({
   key: 'recoil-persist', // this key is using to store data in local storage
   storage: localStorage, // configurate which storage will be used to store the data
+  converter: { // configurate how values will be serialized/deserialized in storage
+    parse: (value) => JSON.parse,
+    stringify: (value) =>  JSON.stringify
+  }
 })
 ```
 
@@ -176,6 +180,22 @@ type config.storage = Storage
 Set `config.storage` with `sessionStorage` or other `Storage` implementation to
 change storage target. Otherwise `localStorage` is used (default).
 
+```js
+type config.converter = {
+  stringify: (value: any) => string
+  parse: (value: string) => any
+}
+```
+
+Set `config.converter` to an object which implements both `stringify` and `parse` functions to convert state values to and from strings. One use of this would be to wrap the standard `JSON.stringify` and `JSON.parse` functions, e.g. to insert your own `reviver` and `replacer` functions:
+
+```js
+{
+  parse: (value) => JSON.parse(value, myCustomReviver),
+  stringify: (value) =>  JSON.stringify(value, myCustomReplacer)
+};
+```
+
 ## Migration from version 1.x.x to 2.x.x
 
 The API changed from version 1.x.x.
diff --git a/src/index.ts b/src/index.ts
index 45d1871..f0c75e2 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -6,9 +6,15 @@ export interface PersistStorage {
   getItem(key: string): null | string | Promise<string>
 }
 
+export interface PersistConverter {
+  stringify: (value: any) => string
+  parse: (value: string) => any
+}
+
 export interface PersistConfiguration {
   key?: string
   storage?: PersistStorage
+  converter?: PersistConverter
 }
 
 /**
@@ -27,7 +33,7 @@ export const recoilPersist = (
     }
   }
 
-  const { key = 'recoil-persist', storage = localStorage } = config
+  const { key = 'recoil-persist', storage = localStorage, converter = JSON } = config
 
   const persistAtom: AtomEffect<any> = ({ onSet, node, trigger, setSelf }) => {
     if (trigger === 'get') {
@@ -89,7 +95,7 @@ export const recoilPersist = (
       return {}
     }
     try {
-      return JSON.parse(state)
+      return converter.parse(state)
     } catch (e) {
       console.error(e)
       return {}
@@ -99,9 +105,9 @@ export const recoilPersist = (
   const setState = (state: any): void => {
     try {
       if (typeof storage.mergeItem === 'function') {
-        storage.mergeItem(key, JSON.stringify(state))
+        storage.mergeItem(key, converter.stringify(state))
       } else {
-        storage.setItem(key, JSON.stringify(state))
+        storage.setItem(key, converter.stringify(state))
       }
     } catch (e) {
       console.error(e)