React Hooks Tic-Tac-Toe

Introduction

React Hooks is a new addition to React version 16.8, allowing to use State in Function. I personally prefer to work with Function over Class in Javascript and now we can do it.
The Idea for this Tutorial is to reproduce the game Tic-Tac-Toe using React Hooks.

Setup

For this tutorial we going to user create-react-app , so be sure to have Nodejs and NPM install in your computer.

In your terminal execute the command:

npx create-react-app tic-tac-toe
cd tic-tac-toe

Now that we create a React App open the directory with a text editor of your choice e.g vim

Create Components

All your source files will be inde de src/ directory. Lets create a new directory for our components.

Inside tic-tac-toe/src create a new /components directory and two new files Table.js and TicBlock.js.
The Table.js going to be a component that going to wrap the TicBlock.js, Ticblock.js are going to be each of the 9 blocks that the user can add X or O.

We need to import Table to our App.js first.

App.js

import React from 'react';
// Allow us to use JXS
import './App.css';
// Import the Style
import Table from './components/Table'
// Import the Table.js components
function App() {
  return (
      <div>
          <Table />
       </div>
  );
}


export default App;
//export in order to be imported by index.js, that is the root file for this App.

If you need more information about the JSX please check this Link.

Know we can edit the Table.js component.
First we need to import the Hook userState and useEffect . Hooks are functions that let you “hook into” React state and lifecycle features from function components¹
For Table we can set three useState, that Table and Table's child will have access.

    const [table, setTable] = useState([0,0,0, 0,0,0, 0,0,0])
    const [winner, setWinner] = useState([])
    const [last, setLast] = useState(Math.random() > 0.5? 5:3)

table and setTable will manage the table state for the X and 0.
winner and setWinner will track the winners
last and setLast will track the last move beeing integer 3 mapping the X
and 5 mapping the O. and set a random last to be 5 or 3.

Now we can use the React Hook useEffect that will run everytime that table state changed.
The useEffect will check if the game is over, if the sum of a row get's to 9,3x3,we X is the winner if
the sum gets 15, 3x5, we know that the O is the winner, and the same applying to diagonal.

    useEffect(()=>{
        //checking winner row and col
        for (let i = 0; i <= 2; i++){
            const idx = (i % 3) * 3 // -> 0,3,6
            //check row
            if ( (table[idx] + table[idx+1] + table[idx+2] )=== 9 || (table[idx] + table[idx+1] + table[idx+2] ) === 15){
                setWinner([idx,idx+1,idx+2])
                gameOver()
            }
            //check col
            if ((table[i] + table[i+3] + table[i+6] )=== 9 || (table[i] + table[i+3] + table[i+6] ) === 15){
                setWinner([i,i+3,i+6])
                gameOver()
            }
        }
        //checking winner diagonal
        if ((table[0] + table[4] + table[8] ) === 15 || (table[0] + table[4] + table[8] ) === 9 ){
            setWinner([0, 4, 8])
            gameOver()
        }
        if ((table[2] + table[4] + table[6] ) === 9 || (table[2] + table[4] + table[6] ) ===15){
            setWinner([2, 4, 6])
            gameOver()
        }
        // check if table completed
        if (table.indexOf(0) === -1){
            gameOver()
        }
    }, [table])

The last argument [table] is the component that React is going to check and run the useEffect
for any update in [table] in this case.

For the blocks we created a component call TicBlock that have an attribute number
that will be unique, last that will receive the last and setLast Hooks and table that
will receive the Hooks table and setTable.

<TicBlock number={0 to 9} last={[last,setLast]} table={[table,setTable]} winner={winner}/> 

For the TicBLock we gonna define get the props for the parent table:

    const number = props.number 
    const [last, setLast] = props.last
    const [table, setTable] = props.table
    const winner = props.winner

So we can use the props to check if we render a empty space, X or O

if is Circle:

<Circle fill={winner.indexOf(number) !== -1? 'red':""} width="100%" height="100%"/>

If is X:

<x fill={winner.indexof(number) !== -1? 'red':""} width="100%" height="100%"/>

Now we need a onClick event listening on the TicBLock and change the
state setTable to X or O:

<div className="ticblock" onClick={() => {
    if (table[number] === 0 && winner.length === 0) {
    setTable(( () => {
        let newTable = [...table];
        let newLast = last === 3? 5:3
        newTable[number] = newLast
        setLast(newLast)
        return newTable
    })())}

You can test the game here.

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1. https://reactjs.org/docs/introducing-jsx.html ↩