Merge pull request #20 from RanzQ/master

Support for replacer and reviver

README.md

@@ -23,6 +23,28 @@ import createEngine from 'redux-storage-engine-localstorage';
 const engine = createEngine('my-save-key');
 ```
 
+You can customize the saving and loading process by providing a [`replacer`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify#The_replacer_parameter) and/or a [`reviver`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse#Using_the_reviver_parameter).
+
+```js
+import createEngine from 'redux-storage-engine-localstorage';
+
+function replacer (key, value) {
+  if (typeof value === 'string') {
+    return 'foo';
+  }
+  return value;
+}
+
+function reviver (key, value) {
+  if (key === 'foo') {
+    return 'bar';
+  }
+  return value;
+});
+
+const engine = createEngine('my-save-key', replacer, reviver);
+```
+
 **Warning**: `localStorage` does not expose a async API and every save/load
 operation will block the JS thread!
 

src/__tests__/index-test.js

@@ -54,6 +54,15 @@ describe('engine', () => {
             return engine.load()
                 .should.eventually.be.rejectedWith('Unexpected token a');
         });
+
+        it('should use a provided reviver', async () => {
+            const reviver = sinon.stub();
+            const engine = createEngine('key', null, reviver);
+
+            await engine.load();
+
+            reviver.should.have.been.called;
+        });
     });
 
     describe('save', () => {
@@ -97,5 +106,14 @@ describe('engine', () => {
             return engine.save(a)
                 .should.eventually.be.rejectedWith('Converting circular structure to JSON');
         });
+
+        it('should use a provided replacer', async () => {
+            const replacer = sinon.stub();
+            const engine = createEngine('key', replacer);
+
+            await engine.save({});
+
+            replacer.should.have.been.called;
+        });
     });
 });

src/index.js

@@ -2,17 +2,17 @@ function rejectWithMessage(error) {
     return Promise.reject(error.message);
 }
 
-export default (key) => ({
+export default (key, replacer, reviver) => ({
     load() {
         return new Promise((resolve) => {
             const jsonState = localStorage.getItem(key);
-            resolve(JSON.parse(jsonState) || {});
+            resolve(JSON.parse(jsonState, reviver) || {});
         }).catch(rejectWithMessage);
     },
 
     save(state) {
         return new Promise((resolve) => {
-            const jsonState = JSON.stringify(state);
+            const jsonState = JSON.stringify(state, replacer);
             localStorage.setItem(key, jsonState);
             resolve();
         }).catch(rejectWithMessage);