Simple Counter

A simple counter is the perfect project web you are in your early steps of learning the React.js library.

We are going to create a visual countdown to showcase the concept of React Components and how you can leverage component properties (props) to reuse those components easily.

A custom component allows you to "divide and conquer", separating logical and visual challenges into smaller pieces- giving you greater control over the display and functionalities of each part of the web-app.

For example, to create a bootstrap <Card /> component you'd code this:

1function Card(props){
2    return (
3        <div className="card">
4            <img className="card-img-top" src="http://via.placeholder.com/350x150" alt="Card image cap" />
5            <div className="card-body">
6                <h5 className="card-title">Card title</h5>
7                <p className="card-text">Some quick example text to build on the card title and fill the card's content.</p>
8                <a href="#" className="btn btn-primary">Go somewhere</a>
9            </div>
10        </div>
11    );
12}

After declaring it, you can import and use it in your webapp like this:

1// Import react into the bundle
2import React from 'react';
3import ReactDOM from 'react-dom';
4import Card from './component/Card.jsx'
5
6const root = ReactDOM.createRoot(document.querySelector('#root'));
7root.render(<App />);
8
9// If you are using a previous version from React v18
10// you have to use ReactDOM.render instead of createRoot
11// like this:
12// ReactDOM.render(<Card />, document.querySelector('#root'));

💡 Note how ReactDOM.createRoot is a function you have to use only one time in your entire application

Additionally, you can pass information through the Card component using props:

1// Use of the custom component
2<Card imageUrl="http://via.placeholder.com/350x150" title="A nice image" />

For usage within the render method of your Card component (notice the image src and card title):

1// Declaration of a custom component (Card.jsx)
2
3function Card(props){
4    return (
5        <div className="card">
6            <img className="card-img-top" src={props.imageUrl} alt="Card image cap" />
7            <div className="card-body">
8                <h5 className="card-title">{props.title}</h5>
9                <p className="card-text">Some quick example text to build on the card title and fill the card's content.</p>
10                <a href="#" className="btn btn-primary">Go somewhere</a>
11            </div>
12        </div>
13    );
14}

🌱 How to start this project

Do not clone this repository because we are going to be using a different template.

We recommend opening the react boilerplate using a provisioning tool like Codespaces (recommended) or Gitpod. Alternatively, you can clone it on your local computer using the git clone command.

This is the repository you need to open or clone:

1https://github.com/4GeeksAcademy/react-hello

👉 Please follow these steps on how to start a coding project.

💡 Important: Remember to save and upload your code to GitHub by creating a new repository, updating the remote (git remote set-url origin <your new url>), and uploading the code to your new repository using the add, commit and push commands from the git terminal.

📝 Instructions

Create a seconds-counter component, called SecondsCounter. It should look like this one.

• The whole purpose of the component is to display how many seconds have passed since the website finished loading (onLoad).
• Use the ReactDOM.createRoot to render the component into the web-app.
• Use the setInterval() function to re-render the component every second.
• The component does not need a local state, you can pass the number of seconds as props, like this:

1<SecondsCounter seconds={3434} />

• You can find the clock icon on the left of the component in Font Awesome.

🔥 Bonus

• Create an option to countdown from a given number.
• Create stop, reset, and resume functionality.
• Create an alert when the user reaches a specified time. If the user enters "10", an alert should render, notifying the user that their time was reached.

This and many other projects are built by students as part of the 4Geeks Academy Coding Bootcamp by Alejandro Sanchez and many other contributors. Find out more about our Full Stack Developer Course, and Data Science Bootcamp.