Allow initial value override

Author: Granipouss

docs/createStateContext.md

@@ -48,9 +48,17 @@ const Demo = () => {
 
 ## Reference
 
-```js
+```jsx
 const [useSharedState, SharedStateProvider] = createStateContext(initialValue);
 
+// In wrapper
+const Wrapper = ({ children }) => (
+  // You can override the initial value for each Provider
+  <SharedStateProvider initialValue={overrideInitialValue}>
+    { children }
+  </SharedStateProvider>
+)
+
 // In a component
 const Component = () => {
   const [sharedState, setSharedState] = useSharedState();

src/createStateContext.ts

@@ -1,11 +1,11 @@
 import { createFactory, createContext, useContext, useState } from 'react';
 
-const createStateContext = <T>(initialValue: T) => {
+const createStateContext = <T>(defaultInitialValue: T) => {
   const context = createContext<[T, React.Dispatch<React.SetStateAction<T>>] | undefined>(undefined);
   const providerFactory = createFactory(context.Provider);
 
-  const StateProvider: React.FC = ({ children }) => {
-    const state = useState<T>(initialValue);
+  const StateProvider: React.FC<{ initialValue?: T }> = ({ children, initialValue }) => {
+    const state = useState<T>(initialValue !== undefined ? initialValue : defaultInitialValue);
     return providerFactory({ value: state }, children);
   };
 

tests/createStateContext.test.tsx

@@ -114,4 +114,19 @@ describe('when using among multiple components', () => {
 
     expect(renderCount).toBe(1);
   });
+
+  it('should override initialValue', () => {
+    const { baseElement } = render(
+      <>
+        <SharedTextProvider>
+          <DisplayComponent />
+        </SharedTextProvider>
+        <SharedTextProvider initialValue={'other'}>
+          <DisplayComponent />
+        </SharedTextProvider>
+      </>
+    );
+
+    expect(baseElement.innerHTML).toBe('<div><p>init</p><p>other</p></div>');
+  });
 });