├── .gitignore
├── README.md
├── jsconfig.json
├── media
    ├── 0-components.png
    ├── 1-counter-state.png
    ├── 2-counter-state.png
    ├── 3-counter-state-props.png
    ├── 4-counter-functions.png
    ├── 5-counter-function-props.png
    └── 6-counter-context.png
├── package-lock.json
├── package.json
├── public
    └── index.html
└── src
    ├── App.css
    ├── App.js
    ├── Counter.js
    ├── index.js
    ├── pages
        ├── Info.js
        └── Login.js
    └── providers
        ├── AuthProvider.js
        └── CounterProvider.js


/.gitignore:
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 1 | # See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
 2 | 
 3 | # dependencies
 4 | /node_modules
 5 | /.pnp
 6 | .pnp.js
 7 | 
 8 | # testing
 9 | /coverage
10 | 
11 | # production
12 | /build
13 | 
14 | # misc
15 | .DS_Store
16 | .env.local
17 | .env.development.local
18 | .env.test.local
19 | .env.production.local
20 | 
21 | npm-debug.log*
22 | yarn-debug.log*
23 | yarn-error.log*
24 | .eslintcache
25 | 


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/README.md:
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 1 | # React Context Demo
 2 | 
 3 | - Prop Drilling
 4 | - React Hooks
 5 | - Context API
 6 | - Context Providers
 7 | - Shared State
 8 | - Interface vs Implementation Functions !!
 9 | 
10 | - Simple Auth / Login App
11 | - Demonstrates Context Providers and useContext
12 | - accepts any username / email address & password
13 | - creates a dummy userId for the newly logged in user
14 | - sets `auth` state if logged in and shows User Info if auth=true
15 | 
16 | - uses `CounterProvider` component to wrap `<Info>` and `<Login`> in `Appjs`
17 | - uses `AuthProvider` component to wrap `<App>` in `index.js`
18 | 
19 | - Do not  share "implementation" functions: `setCounter(), setUser()`.
20 | - Only share "interface" functions:  `increment(), clear(), login()`
21 | - Can share state primitives, just don't share their `setState` functions
22 | - Its generally "OK" to share more complex state objects eg `user`
23 | - Sharing a function is better: `isloggedIn(), getUserName()`
24 | - Avoid deeply nested State.  eg: No `state` object
25 | - Keep your state as flat as possible


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/jsconfig.json:
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1 | {
2 |   "compilerOptions": {
3 |     "baseUrl": "./src"
4 |   }
5 | }
6 | 


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/media/0-components.png:
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https://raw.githubusercontent.com/gary-jipp/demo-react-context/d0feb818481708ee9c0d6ccb82ba5a46b01bab16/media/0-components.png


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/media/1-counter-state.png:
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https://raw.githubusercontent.com/gary-jipp/demo-react-context/d0feb818481708ee9c0d6ccb82ba5a46b01bab16/media/1-counter-state.png


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/media/2-counter-state.png:
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https://raw.githubusercontent.com/gary-jipp/demo-react-context/d0feb818481708ee9c0d6ccb82ba5a46b01bab16/media/2-counter-state.png


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/media/3-counter-state-props.png:
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https://raw.githubusercontent.com/gary-jipp/demo-react-context/d0feb818481708ee9c0d6ccb82ba5a46b01bab16/media/3-counter-state-props.png


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/media/4-counter-functions.png:
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https://raw.githubusercontent.com/gary-jipp/demo-react-context/d0feb818481708ee9c0d6ccb82ba5a46b01bab16/media/4-counter-functions.png


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/media/5-counter-function-props.png:
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https://raw.githubusercontent.com/gary-jipp/demo-react-context/d0feb818481708ee9c0d6ccb82ba5a46b01bab16/media/5-counter-function-props.png


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/media/6-counter-context.png:
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https://raw.githubusercontent.com/gary-jipp/demo-react-context/d0feb818481708ee9c0d6ccb82ba5a46b01bab16/media/6-counter-context.png


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/package.json:
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 1 | {
 2 |   "name": "react-context",
 3 |   "version": "0.1.0",
 4 |   "private": true,
 5 |   "dependencies": {
 6 |     "react": "^17.0.1",
 7 |     "react-dom": "^17.0.1",
 8 |     "react-scripts": "4.0.1"
 9 |   },
10 |   "scripts": {
11 |     "start": "react-scripts start",
12 |     "build": "react-scripts build"
13 |   },
14 |   "browserslist": {
15 |     "production": [
16 |       ">0.2%",
17 |       "not dead",
18 |       "not op_mini all"
19 |     ],
20 |     "development": [
21 |       "last 1 chrome version",
22 |       "last 1 firefox version",
23 |       "last 1 safari version"
24 |     ]
25 |   }
26 | }
27 | 


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/public/index.html:
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 1 | <!DOCTYPE html>
 2 | <html lang="en">
 3 |   <head>
 4 |     <meta charset="utf-8" />
 5 |     <title>React Context Demo</title>
 6 |   </head>
 7 |   <body>
 8 |     <div id="root"></div>
 9 |   </script>
10 |   </body>
11 | </html>
12 | 


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/src/App.css:
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 1 | .UserInfo div {
 2 |   background-color: lightgrey;
 3 |   margin: 1px;
 4 |   /* border: solid 1px; */
 5 |   padding: 0.5em;
 6 |   width: 14em;
 7 | }
 8 | 
 9 | input {
10 |   width: 16em;
11 | }
12 | 
13 | p {
14 |   margin-bottom: 0.5em;
15 |   margin-top: 0.5em;
16 | }
17 | 
18 | span.counter {
19 |   display: inline-block;
20 |   width: 2em;
21 | }
22 | 


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/src/App.js:
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 1 | import Info from 'pages/Info';
 2 | import Login from 'pages/Login';
 3 | import {useAuth} from 'providers/AuthProvider';
 4 | import CounterProvider from 'providers/CounterProvider';
 5 | import 'App.css';
 6 | 
 7 | export default function App() {
 8 |   const {user} = useAuth();
 9 | 
10 |   return (
11 |     <div className="App">
12 |       <CounterProvider>
13 |         <h1>My App</h1>
14 |         {!user && <Login />}
15 |         {!!user && <Info />}
16 |       </CounterProvider>
17 |     </div>
18 |   );
19 | }
20 | 


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/src/Counter.js:
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 1 | import 'App.css';
 2 | import {useCounter} from 'providers/CounterProvider';
 3 | 
 4 | export default function Counter() {
 5 |   const {counter, increment, decrement, clear} = useCounter();
 6 | 
 7 |   return (
 8 |     <div>
 9 |       Counter: <span className="counter"> {counter} </span>
10 |       <button onClick={increment}>+</button>
11 |       <button onClick={clear}>0</button>
12 |       <button onClick={decrement}>-</button>
13 |     </div>
14 |   );
15 | }


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/src/index.js:
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 1 | import React from 'react';
 2 | import ReactDOM from 'react-dom';
 3 | import App from 'App';
 4 | import AuthProvider from 'providers/AuthProvider';
 5 | 
 6 | ReactDOM.render(
 7 |   <AuthProvider>
 8 |     <App />
 9 |   </AuthProvider>,
10 |   document.getElementById('root')
11 | );


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/src/pages/Info.js:
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 1 | import {useAuth} from 'providers/AuthProvider';
 2 | import Counter from 'Counter';
 3 | 
 4 | export default function Info() {
 5 |   const {user, logout} = useAuth();
 6 | 
 7 |   // Show user Info
 8 |   return (
 9 |     <div>
10 |       <Counter />
11 |       <div className="UserInfo">
12 |         <div>You are logged in</div>
13 |         <div>Email: {user.email}</div>
14 |         <div>Name: {user.name}</div>
15 |         <div>UserId: {user.id}</div>
16 |       </div >
17 |       <div>
18 |         <button type="button" onClick={logout}>Logout</button>
19 |       </div>
20 | 
21 |     </div>
22 |   );
23 | };
24 | 


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/src/pages/Login.js:
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 1 | import {useState} from 'react';
 2 | import {useAuth} from 'providers/AuthProvider';
 3 | import Counter from 'Counter';
 4 | 
 5 | export default function Login() {
 6 |   const [email, setEmail] = useState("");
 7 |   const [password, setPassword] = useState("");
 8 |   const {login} = useAuth();
 9 | 
10 |   const onSubmit = function(event) {
11 |     event.preventDefault();
12 |     email && login(email, password);
13 |   };
14 | 
15 |   return (
16 |     <div className="login">
17 |       <Counter />
18 |       <form onSubmit={onSubmit}>
19 |         <div>
20 |           <input type="text" name="username"
21 |             value={email} placeholder="Enter Username or email"
22 |             onChange={event => setEmail(event.target.value)} />
23 |         </div>
24 |         <div>
25 |           <input type="password" name="password"
26 |             value={password} placeholder="Password"
27 |             onChange={event => setPassword(event.target.value)} />
28 |         </div>
29 |         <div className="submit">
30 |           <button type="submit" name="commit">Login</button>
31 |         </div>
32 |       </form>
33 |     </div>
34 |   );
35 | };
36 | 


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/src/providers/AuthProvider.js:
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 1 | import {createContext, useContext, useState} from 'react';
 2 | 
 3 | const context = createContext();
 4 | 
 5 | export const useAuth = function() {
 6 |   return useContext(context);
 7 | };
 8 | 
 9 | export default function AuthProvider(props) {
10 |   const [auth, setAuth] = useState(false);
11 |   const [user, setUser] = useState(null);
12 | 
13 |   // Perform login for the user & save authID, etc
14 |   const login = function(email, password) {
15 |     setAuth(true);
16 |     const id = "1234-1234-1234";  // Some random userId
17 |     setUser({email, id, name: "Test User"});
18 |   };
19 | 
20 |   const logout = function() {
21 |     setAuth(false);
22 |     setUser(null);
23 |   };
24 | 
25 |   // authContext will expose these items
26 |   const value = {auth, user, login, logout};
27 | 
28 |   // We can use this component to wrap any content we want to share this context
29 |   return (
30 |     <context.Provider value={value}>
31 |       {props.children}
32 |     </context.Provider>
33 |   );
34 | };
35 | 


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/src/providers/CounterProvider.js:
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 1 | import {createContext, useContext, useState} from 'react';
 2 | 
 3 | // Create a Context
 4 | const context = createContext();
 5 | 
 6 | // Custom Hook to use Counter Context
 7 | export const useCounter = function() {
 8 |   return useContext(context);
 9 | };
10 | 
11 | // Create a Component wrapper from Context.Provider
12 | export default function CounterProvider(props) {
13 | 
14 |   // Here is our Shared State Object
15 |   const [counter, setCounter] = useState(0);
16 | 
17 |   // Functions to change  the counter state item
18 |   const increment = function() {
19 |     setCounter(counter + 1);
20 |   };
21 |   const decrement = function() {
22 |     setCounter(counter - 1);
23 |   };
24 |   const clear = function() {
25 |     setCounter(0);
26 |   };
27 | 
28 |   // This list can get long with a lot of functions.  Reducer may be a better choice
29 |   const value = {counter, increment, decrement, clear};
30 | 
31 |   // We can now use this as a component to wrap anything
32 |   // that needs our state
33 |   return (
34 |     <context.Provider value={value}>
35 |       {props.children}
36 |     </context.Provider>
37 |   );
38 | };


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