React Workshop

This workshop will teach you how to create a basic React app. The final result will be a rock paper scissors AI

Prerequisite Software

An IDE (Recommend VS Code)
npm (To install 3rd party modules/libraries)
npx (To create a react app)

Steps:

Creating the app

Create a new react app with the following command:
```
npx create-react-app {name of react app}
```
Be sure to replace {name of react app} with your own app name. For this workshop, we will make a rock paper scissors app. Here is the command we will use.
```
npx create-react-app rps-ai
```

Project Architecture

Navigate inside the app directory.
```
cd {app dir}
```
In this example, the command would be
```
cd rps-ai
```
Inside the {app dir}/src directory you will find the following contents:

App.css: Style-sheet for App.js
App.js: This a Component that holds the UI code for the app
App.test.js: This is a test file for App.js. We will not do unit testing in this workshop so we can safely delete it.
index.css: This is the style-sheet that gets applied in index.js
index.js: This is the entry point for the program. App.js should be instantiated in here.
logo.svg: This is a react logo that is added with the create-react-app template. We can safely delete this.
reportWebVitals.js: This will report performance metrics. This is optional, we will leave it in our example.
setupTests.js: This is for setting up unit tests. Let’s delete it for our example.

Here is what the src folder looks like now:

Coding

We are going to use react-bootstrap, a module that will make our UI code simpler. Run the following command to install react-bootstrap:
```
npm i react-bootstrap
```

Now, you need to add the bootstrap stylesheet to your project. To do this, add the following code to {app dir}/public/index.html:

<link
    rel="stylesheet"
    href="https://maxcdn.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css"
    integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T"
    crossorigin="anonymous"
/>

Next, let’s remove the template code so we have a clean slate to work on. Replace the contents of App.js with the following code:

import "./App.css"; // Import our style-sheet

/**
 *  Contains the code for the application
 */
function App() {}

// Makes the App component available to other components.
export default App;

Now we will import some components from bootstrap. Add the following imports to App.js:

import Form from "react-bootstrap/Form";
import Container from "react-bootstrap/Container";
import Row from "react-bootstrap/Row";
import Col from "react-bootstrap/Col";
import Button from "react-bootstrap/Button";

Now we will write the JSX portion of App.js.

/**
 *  Contains the code for the application
 */
function App() {
return (
    <div className="App">
        <Container>
            <h1 className="pb-5">Rock Paper Scissors AI</h1>
            <h3 className="pt-5">Select a difficulty below:</h3>
            <Form.Range min="0" max="100" />
            <Row className="py-5">
                <Col>
                    <Button</Button>
                </Col>
                <Col>
                    <Button></Button>
                </Col>
                <Col>
                    <Button></Button>
                </Col>
            </Row>
        </Container>
    </div>
    );
}

Now we must add the functionality. First we will create some variables. We will use the useState hook to bind our variables to the UI components. First you must import the useState hook.

import { useState } from "react";

Next, add the variables as local variables in the App() function, before the return statement:

function App() {
const [difficulty, setDifficulty] = useState(50.0);
const [winCount, setWinCount] = useState(0);
const [lossCount, setLossCount] = useState(0);
const [result, setResult] = useState(null);

return (
 <div className="App">
   <Container>
     <h1 className="pb-5">Rock Paper Scissors AI</h1>
     <h3 className="pt-5">Select a difficulty below:</h3>
     <Form.Range
       min="0"
       max="100"
       value={difficulty}
       onChange={(e) => setDifficulty(e.target.value)}
     />
     <p>Difficulty: {difficulty}%</p>
     <Row className="py-5">
       <Col>
         <Button></Button>
       </Col>
       <Col>
         <Button></Button>
       </Col>
       <Col>
         <Button></Button>
       </Col>
     </Row>
     <p className="pt-5">{result}</p>
     <Row>
       <Col>Win Count: {winCount}</Col>
       <Col>Loss Count: {lossCount}</Col>
     </Row>
   </Container>
 </div>
);

The last thing we will do is add some logic to control the game.

function App() {
const [difficulty, setDifficulty] = useState(50.0);
const [winCount, setWinCount] = useState(0);
const [lossCount, setLossCount] = useState(0);
const [result, setResult] = useState(null);

function choiceToString(input) {
    switch (input) {
        case 0:
            return "Rock";
        case 1:
            return "Paper";
        default:
            return "Scissors";
    }
}

function choose(input, difficulty) {
    const rand = Math.random();
    if (rand < (difficulty / 50.0) * (1.0 / 3.0)) {
        return (input + 1) % 3;
    } else if (rand < (difficulty / 50.0) * (2.0 / 3.0)) {
        return input;
    } else {
        return (input + 2) % 3;
    }
}

function checkWin(me, ai) {
    if (me === (ai + 1) % 3) {
        setWinCount(winCount + 1);
        return `The opponent chose ${choiceToString(ai)}, you win!`;
    } else if (me === (ai + 2) % 3) {
        setLossCount(lossCount + 1);
        return `The opponent chose ${choiceToString(ai)}, you lose!`;
    } else {
        return `The opponent chose ${choiceToString(ai)}, tie!`;
    }
}

function playGame(input, difficulty) {
    setResult(checkWin(input, choose(input, difficulty)));
}

function difficultyToString(difficulty) {
    if (difficulty < 100.0 / 3.0) {
        return "Easy";
    } else if (difficulty < (2 \* 100.0) / 3.0) {
        return "Medium";
    } else {
        return "Hard";
    }
}

return (
 <div className="App">
   <Container>
     <h1 className="pb-5">Rock Paper Scissors AI</h1>
     <h3 className="pt-5">Select a difficulty below:</h3>
     <Form.Range
       min="0"
       max="100"
       value={difficulty}
       onChange={(e) => setDifficulty(e.target.value)}
     />
     <p>Difficulty: {difficulty}%</p>
     <p className="pb-5">{difficultyToString(difficulty)}</p>
     <Row className="py-5">
       <Col>
         <Button onClick={(e) => playGame(0, difficulty)}>Rock</Button>
       </Col>
       <Col>
         <Button onClick={(e) => playGame(1, difficulty)}>Paper</Button>
       </Col>
       <Col>
         <Button onClick={(e) => playGame(2, difficulty)}>Scissors</Button>
       </Col>
     </Row>
     <p className="pt-5">{result}</p>
     <Row>
       <Col>Win Count: {winCount}</Col>
       <Col>Loss Count: {lossCount}</Col>
     </Row>
   </Container>
 </div>
);
}

The last thing to do is fix the page title. Go into {app dir}/public/index.html and change line 33 to a title of your choose.
```
<title>Rock Paper Scissors AI</title>
```

Final Result

GitHub

View Github