initial work on create slice

src/createSlice.js

@@ -0,0 +1,40 @@
+import { createReducer } from './createReducer';
+
+const getType = (slice, action) =>
+  slice ? `${slice}/${action}` : action;
+
+export default function createSlice({
+  slice = '',
+  actions = {},
+  initialState,
+}) {
+  const actionKeys = Object.keys(actions);
+
+  const reducerMap = actionKeys.reduce(
+    (map, action) => {
+      map[getType(slice, action)] = actions[action];
+      return map;
+    },
+    {},
+  );
+
+  const reducer = createReducer(initialState, reducerMap);
+
+  const actionMap = actionKeys.reduce(
+    (map, action) => {
+      map[action] = (payload) => ({
+        type: getType(slice, action),
+        payload,
+      });
+
+      return map;
+    },
+    {},
+  );
+
+  return {
+    actions: actionMap,
+    reducer,
+    slice,
+  };
+}

src/createSlice.test.js

@@ -0,0 +1,86 @@
+import createSlice from './createSlice'
+
+describe('createSlice', () => {
+  describe('when slice is empty', () => {
+    const { actions, reducer } = createSlice({
+      actions: {
+        increment: state => state + 1,
+        multiply: (state, action) => state * action.payload
+      },
+      initialState: 0
+    })
+
+    it('should create increment action', () => {
+      expect(actions.hasOwnProperty('increment')).toBe(true)
+    })
+
+    it('should create multiply action', () => {
+      expect(actions.hasOwnProperty('multiply')).toBe(true)
+    })
+
+    it('should have the correct action for increment', () => {
+      expect(actions.increment()).toEqual({
+        type: 'increment',
+        payload: undefined
+      })
+    })
+
+    it('should have the correct action for multiply', () => {
+      expect(actions.multiply(3)).toEqual({
+        type: 'multiply',
+        payload: 3
+      })
+    })
+
+    describe('when using reducer', () => {
+      it('should return the correct value from reducer with increment', () => {
+        expect(reducer(undefined, actions.increment())).toEqual(1)
+      })
+
+      it('should return the correct value from reducer with multiply', () => {
+        expect(reducer(2, actions.multiply(3))).toEqual(6)
+      })
+    })
+  })
+
+  describe('when passing slice', () => {
+    const { actions, reducer } = createSlice({
+      actions: {
+        increment: state => state + 1
+      },
+      initialState: 0,
+      slice: 'cool'
+    })
+
+    it('should create increment action', () => {
+      expect(actions.hasOwnProperty('increment')).toBe(true)
+    })
+
+    it('should have the correct action for increment', () => {
+      expect(actions.increment()).toEqual({
+        type: 'cool/increment',
+        payload: undefined
+      })
+    })
+
+    it('should return the correct value from reducer', () => {
+      expect(reducer(undefined, actions.increment())).toEqual(1)
+    })
+  })
+
+  describe('when mutating state object', () => {
+    const { actions, reducer } = createSlice({
+      actions: {
+        setUserName: (state, action) => {
+          state.user = action.payload
+        }
+      },
+      initialState: { user: '' },
+      slice: 'user'
+    })
+
+    it('should set the username', () => {
+      expect(reducer({}, actions.setUserName('eric'))).toEqual({ user: 'eric' })
+    })
+  })
+})

src/index.js

@@ -1,5 +1,6 @@
 export { configureStore, getDefaultMiddleware } from './configureStore'
 export { createReducer } from './createReducer'
+export { default as createSlice } from './createSlice';
 
 export { default as createNextState } from 'immer'
 export { combineReducers, compose } from 'redux'