adding docs subtree

2026-01-26 14:56:42 +08:00 · 2019-02-25 13:12:18 -08:00
parent 1adcc07a61
commit 41dcf8731d
365 changed files with 10620 additions and 0 deletions
--- a/docs/step2-08/README.md
+++ b/docs/step2-08/README.md
@@ -0,0 +1,72 @@
+# Step 2.8
+
+[Lessons](../) | [Exercise](./exercise/) | [Demo](./demo/)
+
+Combine Reducers
+
+This lesson is just a helper to make the process of writing reducers use less boilerplate code. This step briefly introduces to a world of helpers in writing Redux code.
+
+Our Redux store so far has this shape, roughly:
+
+```js
+const state = {
+  todos: {
+    id0: {
+      label: 'hello',
+      completed: false
+    },
+    id1: {
+      label: 'world',
+      completed: true
+    }
+  },
+
+  filter: 'all'
+};
+```
+
+As the application grows in complexity, so will the shape of the store. Currently, the store captures two separate but related ideas: the todo items and the selected filter. The reducers should follow the shape of the store. Think of reducers as part of the store itself and are responsible to update a single part of the store based on actions that they receive as a second argument. As complexity of state grows, we split these reducers:
+
+```ts
+function todoReducer(state: Store['todos'] = {}, action: any) {
+  // reduce on the todos part of the state tree
+}
+
+function filterReducer(state: Store['filter'] = 'all', action: any) {
+  // reduce on the filter flag
+}
+
+// Then use the redux-provided combineReducers() to combine them
+export const reducer = combineReducers({
+  todos: todoReducer,
+  filter: filterReducer
+});
+```
+
+`combineReducers` handles the grunt-work of sending *actions* to each combined reducer. Therefore, when an action arrives, each reducer is given the opportunity to modify its own state tree based on the incoming action.
+
+# Exercise
+
+1. open up `exercise/src/reducers/index.ts`
+
+2. implement the `filterReducer` function with a switch / case statement - it is contrived to have a switch case for ONE condition, but serves to be a good exercise here
+
+3. replace the export reducer function with the help of the `combineReducer()` function from `redux`
+
+# Bonus Exercise
+
+The Redux team came up with `redux-starter-kit` to address a lot of boilerplate concerns. They also embed the immer library to make it nicer to write reducer functions. So, let's try out `immer`! Look at this example: https://github.com/mweststrate/immer#reducer-example
+
+1. import immer into the `exercise/src/reducers/pureFunction.ts` file
+
+2. replace the implementation of the pure functions with the help of immer's `produce()`
+
+3. run `npm test` in the root folder to see if it still works!
+
+4. look at the web app to make sure it still works!
+
+# Further reading
+
+- immer: https://github.com/mweststrate/immer - improves ergonomics of working with immutables by introducing the concept of mutating a draft
+
+- redux-starter-kit: https://github.com/reduxjs/redux-starter-kit - help address common concerns of Redux in boilerplate and complexity
--- a/docs/step2-08/demo/index.html
+++ b/docs/step2-08/demo/index.html
@@ -0,0 +1 @@
+<!doctype html><html><head><link rel="stylesheet" href="../../assets/step.css"></head><body class="ms-Fabric"><div id="markdownReadme"></div><div id="app"></div><script src="../../step2-08/demo/step2-08/demo.js"></script><script src="../../markdownReadme/markdownReadme.js"></script></body></html>
--- a/docs/step2-08/demo/src/actions/index.ts
+++ b/docs/step2-08/demo/src/actions/index.ts
@@ -0,0 +1,9 @@
+import uuid from 'uuid/v4';
+
+export const actions = {
+  addTodo: (label: string) => ({ type: 'addTodo', id: uuid(), label }),
+  remove: (id: string) => ({ type: 'remove', id }),
+  complete: (id: string) => ({ type: 'complete', id }),
+  clear: () => ({ type: 'clear' }),
+  setFilter: (filter: string) => ({ type: 'setFilter', filter })
+};
--- a/docs/step2-08/demo/src/components/TodoApp.tsx
+++ b/docs/step2-08/demo/src/components/TodoApp.tsx
@@ -0,0 +1,26 @@
+import React from 'react';
+import { Stack, Customizer, mergeStyles, getTheme } from 'office-ui-fabric-react';
+import { TodoFooter } from './TodoFooter';
+import { TodoHeader } from './TodoHeader';
+import { TodoList } from './TodoList';
+import { Store } from '../store';
+import { FluentCustomizations } from '@uifabric/fluent-theme';
+
+const className = mergeStyles({
+  padding: 25,
+  ...getTheme().effects.elevation4
+});
+
+export const TodoApp = () => {
+  return (
+    <Customizer {...FluentCustomizations}>
+      <Stack horizontalAlign="center">
+        <Stack style={{ width: 400 }} gap={25} className={className}>
+          <TodoHeader />
+          <TodoList />
+          <TodoFooter />
+        </Stack>
+      </Stack>
+    </Customizer>
+  );
+};
--- a/docs/step2-08/demo/src/components/TodoFooter.tsx
+++ b/docs/step2-08/demo/src/components/TodoFooter.tsx
@@ -0,0 +1,42 @@
+import React from 'react';
+import { Text } from '@uifabric/experiments';
+import { Stack } from 'office-ui-fabric-react';
+import { Store } from '../store';
+import { DefaultButton } from 'office-ui-fabric-react';
+import { connect } from 'react-redux';
+import { actions } from '../actions';
+
+interface TodoFooterProps {
+  clear: () => void;
+  todos: Store['todos'];
+}
+
+const TodoFooter = (props: TodoFooterProps) => {
+  const itemCount = Object.keys(props.todos).filter(id => !props.todos[id].completed).length;
+
+  return (
+    <Stack horizontal horizontalAlign="space-between">
+      <Text>
+        {itemCount} item{itemCount > 1 ? 's' : ''} left
+      </Text>
+      <DefaultButton onClick={() => props.clear()}>Clear Completed</DefaultButton>
+    </Stack>
+  );
+};
+
+function mapStateToProps(state: Store) {
+  return { ...state };
+}
+
+function mapDispatchToProps(dispatch: any) {
+  return {
+    clear: () => dispatch(actions.clear())
+  };
+}
+
+const component = connect(
+  mapStateToProps,
+  mapDispatchToProps
+)(TodoFooter);
+
+export { component as TodoFooter };
--- a/docs/step2-08/demo/src/components/TodoHeader.tsx
+++ b/docs/step2-08/demo/src/components/TodoHeader.tsx
@@ -0,0 +1,78 @@
+import React from 'react';
+import { Text } from '@uifabric/experiments';
+import { Stack } from 'office-ui-fabric-react';
+import { Pivot, PivotItem, TextField, PrimaryButton } from 'office-ui-fabric-react';
+import { FilterTypes, Store } from '../store';
+import { actions } from '../actions';
+import { connect } from 'react-redux';
+
+interface TodoHeaderProps {
+  addTodo: (label: string) => void;
+  setFilter: (filter: FilterTypes) => void;
+  filter: FilterTypes;
+}
+
+interface TodoHeaderState {
+  labelInput: string;
+}
+
+class TodoHeader extends React.Component<TodoHeaderProps, TodoHeaderState> {
+  constructor(props: TodoHeaderProps) {
+    super(props);
+    this.state = { labelInput: undefined };
+  }
+
+  render() {
+    return (
+      <Stack gap={10}>
+        <Stack horizontal horizontalAlign="center">
+          <Text variant="xxLarge">todos</Text>
+        </Stack>
+
+        <Stack horizontal gap={10}>
+          <Stack.Item grow>
+            <TextField placeholder="What needs to be done?" value={this.state.labelInput} onChange={this.onChange} />
+          </Stack.Item>
+          <PrimaryButton onClick={this.onAdd}>Add</PrimaryButton>
+        </Stack>
+
+        <Pivot onLinkClick={this.onFilter}>
+          <PivotItem headerText="all" />
+          <PivotItem headerText="active" />
+          <PivotItem headerText="completed" />
+        </Pivot>
+      </Stack>
+    );
+  }
+
+  private onAdd = () => {
+    this.props.addTodo(this.state.labelInput);
+    this.setState({ labelInput: undefined });
+  };
+
+  private onChange = (evt: React.FormEvent<HTMLInputElement>, newValue: string) => {
+    this.setState({ labelInput: newValue });
+  };
+
+  private onFilter = (item: PivotItem) => {
+    this.props.setFilter(item.props.headerText as FilterTypes);
+  };
+}
+
+function mapStateToProps(state: Store) {
+  return { ...state };
+}
+
+function mapDispatchToProps(dispatch: any) {
+  return {
+    addTodo: (label: string) => dispatch(actions.addTodo(label)),
+    setFilter: (filter: FilterTypes) => dispatch(actions.setFilter(filter))
+  };
+}
+
+const component = connect(
+  mapStateToProps,
+  mapDispatchToProps
+)(TodoHeader);
+
+export { component as TodoHeader };
--- a/docs/step2-08/demo/src/components/TodoList.tsx
+++ b/docs/step2-08/demo/src/components/TodoList.tsx
@@ -0,0 +1,40 @@
+import React from 'react';
+import { Stack } from 'office-ui-fabric-react';
+import { TodoListItem } from './TodoListItem';
+import { Store, FilterTypes } from '../store';
+import { connect } from 'react-redux';
+
+interface TodoListProps {
+  todos: Store['todos'];
+  filter: FilterTypes;
+}
+
+const TodoList = (props: TodoListProps) => {
+  const { filter, todos } = props;
+  const filteredTodos = Object.keys(todos).filter(id => {
+    return filter === 'all' || (filter === 'completed' && todos[id].completed) || (filter === 'active' && !todos[id].completed);
+  });
+
+  return (
+    <Stack gap={10}>
+      {filteredTodos.map(id => (
+        <TodoListItem key={id} id={id} />
+      ))}
+    </Stack>
+  );
+};
+
+function mapStateToProps(state: Store) {
+  return { ...state };
+}
+
+function mapDispatchToProps(dispatch: any) {
+  return {};
+}
+
+const component = connect(
+  mapStateToProps,
+  mapDispatchToProps
+)(TodoList);
+
+export { component as TodoList };
--- a/docs/step2-08/demo/src/components/TodoListItem.tsx
+++ b/docs/step2-08/demo/src/components/TodoListItem.tsx
@@ -0,0 +1,48 @@
+import React from 'react';
+import { Stack, Checkbox, IconButton } from 'office-ui-fabric-react';
+import { Store } from '../store';
+import { connect } from 'react-redux';
+import { actions } from '../actions';
+
+interface TodoListItemProps {
+  id: string;
+  todos: Store['todos'];
+  remove: (id: string) => void;
+  complete: (id: string) => void;
+}
+
+class TodoListItem extends React.Component<TodoListItemProps, {}> {
+  render() {
+    const { todos, id, complete, remove } = this.props;
+    const item = todos[id];
+
+    return (
+      <Stack horizontal verticalAlign="center" horizontalAlign="space-between">
+        <Checkbox label={item.label} checked={item.completed} onChange={() => complete(id)} />
+        <div>
+          <IconButton iconProps={{ iconName: 'Cancel' }} onClick={() => remove(id)} />
+        </div>
+      </Stack>
+    );
+  }
+}
+
+function mapStateToProps({ todos }: Store) {
+  return {
+    todos
+  };
+}
+
+function mapDispatchToProps(dispatch: any) {
+  return {
+    remove: (id: string) => dispatch(actions.remove(id)),
+    complete: (id: string) => dispatch(actions.complete(id))
+  };
+}
+
+const component = connect(
+  mapStateToProps,
+  mapDispatchToProps
+)(TodoListItem);
+
+export { component as TodoListItem };
--- a/docs/step2-08/demo/src/index.tsx
+++ b/docs/step2-08/demo/src/index.tsx
@@ -0,0 +1,23 @@
+import React from 'react';
+import ReactDOM from 'react-dom';
+import { reducer } from './reducers';
+import { createStore } from 'redux';
+import { Provider } from 'react-redux';
+import { TodoApp } from './components/TodoApp';
+import { actions } from './actions';
+import { initializeIcons } from '@uifabric/icons';
+import { composeWithDevTools } from 'redux-devtools-extension';
+
+const store = createStore(reducer, {}, composeWithDevTools());
+
+store.dispatch(actions.addTodo('hello'));
+store.dispatch(actions.addTodo('world'));
+
+initializeIcons();
+
+ReactDOM.render(
+  <Provider store={store}>
+    <TodoApp />
+  </Provider>,
+  document.getElementById('app')
+);
--- a/docs/step2-08/demo/src/reducers/index.ts
+++ b/docs/step2-08/demo/src/reducers/index.ts
@@ -0,0 +1,35 @@
+import { Store } from '../store';
+import { addTodo, remove, complete, clear, setFilter } from './pureFunctions';
+import { combineReducers } from 'redux';
+
+function todoReducer(state: Store['todos'] = {}, action: any): Store['todos'] {
+  switch (action.type) {
+    case 'addTodo':
+      return addTodo(state, action.id, action.label);
+
+    case 'remove':
+      return remove(state, action.id);
+
+    case 'clear':
+      return clear(state);
+
+    case 'complete':
+      return complete(state, action.id);
+  }
+
+  return state;
+}
+
+function filterReducer(state: Store['filter'] = 'all', action: any): Store['filter'] {
+  switch (action.type) {
+    case 'setFilter':
+      return setFilter(state, action.filter);
+  }
+
+  return state;
+}
+
+export const reducer = combineReducers({
+  todos: todoReducer,
+  filter: filterReducer
+});
--- a/docs/step2-08/demo/src/reducers/pureFunctions.spec.ts
+++ b/docs/step2-08/demo/src/reducers/pureFunctions.spec.ts
@@ -0,0 +1,29 @@
+import { addTodo, complete } from './pureFunctions';
+import { Store } from '../store';
+
+describe('TodoApp reducers', () => {
+  it('can add an item', () => {
+    const state = <Store['todos']>{};
+
+    const newState = addTodo(state, '0', 'item1');
+
+    const keys = Object.keys(newState);
+
+    expect(newState).not.toBe(state);
+    expect(keys.length).toBe(1);
+    expect(newState[keys[0]].label).toBe('item1');
+    expect(newState[keys[0]].completed).toBeFalsy();
+  });
+
+  it('can complete an item', () => {
+    const state = <Store['todos']>{};
+
+    let newState = addTodo(state, '0', 'item1');
+
+    const key = Object.keys(newState)[0];
+
+    newState = complete(newState, key);
+
+    expect(newState[key].completed).toBeTruthy();
+  });
+});
--- a/docs/step2-08/demo/src/reducers/pureFunctions.ts
+++ b/docs/step2-08/demo/src/reducers/pureFunctions.ts
@@ -0,0 +1,36 @@
+import { Store, FilterTypes } from '../store';
+
+export function addTodo(state: Store['todos'], id: string, label: string): Store['todos'] {
+  return { ...state, [id]: { label, completed: false } };
+}
+
+export function remove(state: Store['todos'], id: string) {
+  const newTodos = { ...state };
+
+  delete newTodos[id];
+
+  return newTodos;
+}
+
+export function complete(state: Store['todos'], id: string) {
+  const newTodos = { ...state };
+  newTodos[id].completed = !newTodos[id].completed;
+
+  return newTodos;
+}
+
+export function clear(state: Store['todos']) {
+  const newTodos = { ...state };
+
+  Object.keys(state.todos).forEach(key => {
+    if (state.todos[key].completed) {
+      delete newTodos[key];
+    }
+  });
+
+  return newTodos;
+}
+
+export function setFilter(state: Store['filter'], filter: FilterTypes) {
+  return filter;
+}
--- a/docs/step2-08/demo/src/store/index.ts
+++ b/docs/step2-08/demo/src/store/index.ts
@@ -0,0 +1,14 @@
+export type FilterTypes = 'all' | 'active' | 'completed';
+
+export interface TodoItem {
+  label: string;
+  completed: boolean;
+}
+
+export interface Store {
+  todos: {
+    [id: string]: TodoItem;
+  };
+
+  filter: FilterTypes;
+}
--- a/docs/step2-08/demo/step2-08/demo.js
+++ b/docs/step2-08/demo/step2-08/demo.js
--- a/docs/step2-08/demo/step2-08/demo.js.map
+++ b/docs/step2-08/demo/step2-08/demo.js.map
--- a/docs/step2-08/exercise/index.html
+++ b/docs/step2-08/exercise/index.html
@@ -0,0 +1 @@
+<!doctype html><html><head><link rel="stylesheet" href="../../assets/step.css"></head><body class="ms-Fabric"><div id="markdownReadme"></div><div id="app"></div><script src="../../step2-08/exercise/step2-08/exercise.js"></script><script src="../../markdownReadme/markdownReadme.js"></script></body></html>
--- a/docs/step2-08/exercise/src/actions/index.ts
+++ b/docs/step2-08/exercise/src/actions/index.ts
@@ -0,0 +1,9 @@
+import uuid from 'uuid/v4';
+
+export const actions = {
+  addTodo: (label: string) => ({ type: 'addTodo', id: uuid(), label }),
+  remove: (id: string) => ({ type: 'remove', id }),
+  complete: (id: string) => ({ type: 'complete', id }),
+  clear: () => ({ type: 'clear' }),
+  setFilter: (filter: string) => ({ type: 'setFilter', filter })
+};
--- a/docs/step2-08/exercise/src/components/TodoApp.tsx
+++ b/docs/step2-08/exercise/src/components/TodoApp.tsx
@@ -0,0 +1,26 @@
+import React from 'react';
+import { Stack, Customizer, mergeStyles, getTheme } from 'office-ui-fabric-react';
+import { TodoFooter } from './TodoFooter';
+import { TodoHeader } from './TodoHeader';
+import { TodoList } from './TodoList';
+import { Store } from '../store';
+import { FluentCustomizations } from '@uifabric/fluent-theme';
+
+const className = mergeStyles({
+  padding: 25,
+  ...getTheme().effects.elevation4
+});
+
+export const TodoApp = () => {
+  return (
+    <Customizer {...FluentCustomizations}>
+      <Stack horizontalAlign="center">
+        <Stack style={{ width: 400 }} gap={25} className={className}>
+          <TodoHeader />
+          <TodoList />
+          <TodoFooter />
+        </Stack>
+      </Stack>
+    </Customizer>
+  );
+};
--- a/docs/step2-08/exercise/src/components/TodoFooter.tsx
+++ b/docs/step2-08/exercise/src/components/TodoFooter.tsx
@@ -0,0 +1,42 @@
+import React from 'react';
+import { Text } from '@uifabric/experiments';
+import { Stack } from 'office-ui-fabric-react';
+import { Store } from '../store';
+import { DefaultButton } from 'office-ui-fabric-react';
+import { connect } from 'react-redux';
+import { actions } from '../actions';
+
+interface TodoFooterProps {
+  clear: () => void;
+  todos: Store['todos'];
+}
+
+const TodoFooter = (props: TodoFooterProps) => {
+  const itemCount = Object.keys(props.todos).filter(id => !props.todos[id].completed).length;
+
+  return (
+    <Stack horizontal horizontalAlign="space-between">
+      <Text>
+        {itemCount} item{itemCount > 1 ? 's' : ''} left
+      </Text>
+      <DefaultButton onClick={() => props.clear()}>Clear Completed</DefaultButton>
+    </Stack>
+  );
+};
+
+function mapStateToProps(state: Store) {
+  return { ...state };
+}
+
+function mapDispatchToProps(dispatch: any) {
+  return {
+    clear: () => dispatch(actions.clear())
+  };
+}
+
+const component = connect(
+  mapStateToProps,
+  mapDispatchToProps
+)(TodoFooter);
+
+export { component as TodoFooter };
--- a/docs/step2-08/exercise/src/components/TodoHeader.tsx
+++ b/docs/step2-08/exercise/src/components/TodoHeader.tsx
@@ -0,0 +1,78 @@
+import React from 'react';
+import { Text } from '@uifabric/experiments';
+import { Stack } from 'office-ui-fabric-react';
+import { Pivot, PivotItem, TextField, PrimaryButton } from 'office-ui-fabric-react';
+import { FilterTypes, Store } from '../store';
+import { actions } from '../actions';
+import { connect } from 'react-redux';
+
+interface TodoHeaderProps {
+  addTodo: (label: string) => void;
+  setFilter: (filter: FilterTypes) => void;
+  filter: FilterTypes;
+}
+
+interface TodoHeaderState {
+  labelInput: string;
+}
+
+class TodoHeader extends React.Component<TodoHeaderProps, TodoHeaderState> {
+  constructor(props: TodoHeaderProps) {
+    super(props);
+    this.state = { labelInput: undefined };
+  }
+
+  render() {
+    return (
+      <Stack gap={10}>
+        <Stack horizontal horizontalAlign="center">
+          <Text variant="xxLarge">todos</Text>
+        </Stack>
+
+        <Stack horizontal gap={10}>
+          <Stack.Item grow>
+            <TextField placeholder="What needs to be done?" value={this.state.labelInput} onChange={this.onChange} />
+          </Stack.Item>
+          <PrimaryButton onClick={this.onAdd}>Add</PrimaryButton>
+        </Stack>
+
+        <Pivot onLinkClick={this.onFilter}>
+          <PivotItem headerText="all" />
+          <PivotItem headerText="active" />
+          <PivotItem headerText="completed" />
+        </Pivot>
+      </Stack>
+    );
+  }
+
+  private onAdd = () => {
+    this.props.addTodo(this.state.labelInput);
+    this.setState({ labelInput: undefined });
+  };
+
+  private onChange = (evt: React.FormEvent<HTMLInputElement>, newValue: string) => {
+    this.setState({ labelInput: newValue });
+  };
+
+  private onFilter = (item: PivotItem) => {
+    this.props.setFilter(item.props.headerText as FilterTypes);
+  };
+}
+
+function mapStateToProps(state: Store) {
+  return { ...state };
+}
+
+function mapDispatchToProps(dispatch: any) {
+  return {
+    addTodo: (label: string) => dispatch(actions.addTodo(label)),
+    setFilter: (filter: FilterTypes) => dispatch(actions.setFilter(filter))
+  };
+}
+
+const component = connect(
+  mapStateToProps,
+  mapDispatchToProps
+)(TodoHeader);
+
+export { component as TodoHeader };
--- a/docs/step2-08/exercise/src/components/TodoList.tsx
+++ b/docs/step2-08/exercise/src/components/TodoList.tsx
@@ -0,0 +1,40 @@
+import React from 'react';
+import { Stack } from 'office-ui-fabric-react';
+import { TodoListItem } from './TodoListItem';
+import { Store, FilterTypes } from '../store';
+import { connect } from 'react-redux';
+
+interface TodoListProps {
+  todos: Store['todos'];
+  filter: FilterTypes;
+}
+
+const TodoList = (props: TodoListProps) => {
+  const { filter, todos } = props;
+  const filteredTodos = Object.keys(todos).filter(id => {
+    return filter === 'all' || (filter === 'completed' && todos[id].completed) || (filter === 'active' && !todos[id].completed);
+  });
+
+  return (
+    <Stack gap={10}>
+      {filteredTodos.map(id => (
+        <TodoListItem key={id} id={id} />
+      ))}
+    </Stack>
+  );
+};
+
+function mapStateToProps(state: Store) {
+  return { ...state };
+}
+
+function mapDispatchToProps(dispatch: any) {
+  return {};
+}
+
+const component = connect(
+  mapStateToProps,
+  mapDispatchToProps
+)(TodoList);
+
+export { component as TodoList };
--- a/docs/step2-08/exercise/src/components/TodoListItem.tsx
+++ b/docs/step2-08/exercise/src/components/TodoListItem.tsx
@@ -0,0 +1,48 @@
+import React from 'react';
+import { Stack, Checkbox, IconButton } from 'office-ui-fabric-react';
+import { Store } from '../store';
+import { connect } from 'react-redux';
+import { actions } from '../actions';
+
+interface TodoListItemProps {
+  id: string;
+  todos: Store['todos'];
+  remove: (id: string) => void;
+  complete: (id: string) => void;
+}
+
+class TodoListItem extends React.Component<TodoListItemProps, {}> {
+  render() {
+    const { todos, id, complete, remove } = this.props;
+    const item = todos[id];
+
+    return (
+      <Stack horizontal verticalAlign="center" horizontalAlign="space-between">
+        <Checkbox label={item.label} checked={item.completed} onChange={() => complete(id)} />
+        <div>
+          <IconButton iconProps={{ iconName: 'Cancel' }} onClick={() => remove(id)} />
+        </div>
+      </Stack>
+    );
+  }
+}
+
+function mapStateToProps({ todos }: Store) {
+  return {
+    todos
+  };
+}
+
+function mapDispatchToProps(dispatch: any) {
+  return {
+    remove: (id: string) => dispatch(actions.remove(id)),
+    complete: (id: string) => dispatch(actions.complete(id))
+  };
+}
+
+const component = connect(
+  mapStateToProps,
+  mapDispatchToProps
+)(TodoListItem);
+
+export { component as TodoListItem };
--- a/docs/step2-08/exercise/src/index.tsx
+++ b/docs/step2-08/exercise/src/index.tsx
@@ -0,0 +1,23 @@
+import React from 'react';
+import ReactDOM from 'react-dom';
+import { reducer } from './reducers';
+import { createStore } from 'redux';
+import { Provider } from 'react-redux';
+import { TodoApp } from './components/TodoApp';
+import { actions } from './actions';
+import { initializeIcons } from '@uifabric/icons';
+import { composeWithDevTools } from 'redux-devtools-extension';
+
+const store = createStore(reducer, {}, composeWithDevTools());
+
+store.dispatch(actions.addTodo('hello'));
+store.dispatch(actions.addTodo('world'));
+
+initializeIcons();
+
+ReactDOM.render(
+  <Provider store={store}>
+    <TodoApp />
+  </Provider>,
+  document.getElementById('app')
+);
--- a/docs/step2-08/exercise/src/reducers/index.ts
+++ b/docs/step2-08/exercise/src/reducers/index.ts
@@ -0,0 +1,35 @@
+import { Store } from '../store';
+import { addTodo, remove, complete, clear, setFilter } from './pureFunctions';
+import { combineReducers } from 'redux';
+
+function todoReducer(state: Store['todos'] = {}, action: any): Store['todos'] {
+  switch (action.type) {
+    case 'addTodo':
+      return addTodo(state, action.id, action.label);
+
+    case 'remove':
+      return remove(state, action.id);
+
+    case 'clear':
+      return clear(state);
+
+    case 'complete':
+      return complete(state, action.id);
+  }
+
+  return state;
+}
+
+function filterReducer(state: Store['filter'] = 'all', action: any): Store['filter'] {
+  // TODO: fill in the blank here with a switch / case statement to return new filter state as specified in `action.filter` message
+
+  return state;
+}
+
+// TODO: rewrite this reducer function with combineReducer() helper
+export function reducer(state: Store, action: any): Store {
+  return {
+    todos: todoReducer(state.todos, action),
+    filter: 'all'
+  };
+}
--- a/docs/step2-08/exercise/src/reducers/pureFunctions.spec.ts
+++ b/docs/step2-08/exercise/src/reducers/pureFunctions.spec.ts
@@ -0,0 +1,29 @@
+import { addTodo, complete } from './pureFunctions';
+import { Store } from '../store';
+
+describe('TodoApp reducers', () => {
+  it('can add an item', () => {
+    const state = <Store['todos']>{};
+
+    const newState = addTodo(state, '0', 'item1');
+
+    const keys = Object.keys(newState);
+
+    expect(newState).not.toBe(state);
+    expect(keys.length).toBe(1);
+    expect(newState[keys[0]].label).toBe('item1');
+    expect(newState[keys[0]].completed).toBeFalsy();
+  });
+
+  it('can complete an item', () => {
+    const state = <Store['todos']>{};
+
+    let newState = addTodo(state, '0', 'item1');
+
+    const key = Object.keys(newState)[0];
+
+    newState = complete(newState, key);
+
+    expect(newState[key].completed).toBeTruthy();
+  });
+});
--- a/docs/step2-08/exercise/src/reducers/pureFunctions.ts
+++ b/docs/step2-08/exercise/src/reducers/pureFunctions.ts
@@ -0,0 +1,48 @@
+import { Store, FilterTypes } from '../store';
+
+import produce from 'immer';
+
+export function addTodo(state: Store['todos'], id: string, label: string): Store['todos'] {
+  return { ...state, [id]: { label, completed: false } };
+}
+
+/* For the bonus exercise
+
+export function addTodo(state: Store['todos'], id: string, label: string): Store['todos'] {
+  return produce(state, draft => {
+    // TODO: implement a simple obj key assignment here
+  });
+}
+
+*/
+
+export function remove(state: Store['todos'], id: string) {
+  const newTodos = { ...state };
+
+  delete newTodos[id];
+
+  return newTodos;
+}
+
+export function complete(state: Store['todos'], id: string) {
+  const newTodos = { ...state };
+  newTodos[id].completed = !newTodos[id].completed;
+
+  return newTodos;
+}
+
+export function clear(state: Store['todos']) {
+  const newTodos = { ...state };
+
+  Object.keys(state.todos).forEach(key => {
+    if (state.todos[key].completed) {
+      delete newTodos[key];
+    }
+  });
+
+  return newTodos;
+}
+
+export function setFilter(state: Store['filter'], filter: FilterTypes) {
+  return filter;
+}
--- a/docs/step2-08/exercise/src/store/index.ts
+++ b/docs/step2-08/exercise/src/store/index.ts
@@ -0,0 +1,14 @@
+export type FilterTypes = 'all' | 'active' | 'completed';
+
+export interface TodoItem {
+  label: string;
+  completed: boolean;
+}
+
+export interface Store {
+  todos: {
+    [id: string]: TodoItem;
+  };
+
+  filter: FilterTypes;
+}
--- a/docs/step2-08/exercise/step2-08/exercise.js
+++ b/docs/step2-08/exercise/step2-08/exercise.js
--- a/docs/step2-08/exercise/step2-08/exercise.js.map
+++ b/docs/step2-08/exercise/step2-08/exercise.js.map
				`@@ -0,0 +1 @@`
				`<!doctype html><html><head><link rel="stylesheet" href="../../assets/step.css"></head><body class="ms-Fabric"><div id="markdownReadme"></div><div id="app"></div><script src="../../step2-08/demo/step2-08/demo.js"></script><script src="../../markdownReadme/markdownReadme.js"></script></body></html>`