01. Stopwatch/Count-Up Timer || Learn React Through Mini Projects

Summary

This tutorial demonstrates how to build a simple React stopwatch app in under 20 minutes. It covers setting up the project, using React hooks like useState, performing calculations, adding start/stop/reset buttons, utilizing useEffect for side effects, and applying basic Tailwind CSS for styling.

Takeaways

• 🛠️ Start by setting up a React project using `create-react-app` and name it 'stopwatch'.
• ⏱ Use the `useState` hook to track the stopwatch's time and provide a method to update it.
• 📝 Destructure the `useState` return value to get the current state and the function to update it, initializing with zero.
• 🔢 Calculate the stopwatch display time by dividing the milliseconds and using the remainder operator to format minutes and seconds.
• 🔴 Add buttons for start, stop, and reset functionalities, updating the 'running' state accordingly.
• 🔁 Use the `useEffect` hook to handle side effects like starting and stopping the timer with `setInterval` and `clearInterval`.
• ✂️ Include the 'running' state in the `useEffect` dependencies to ensure the timer stops when the component unmounts.
• 🔄 Implement conditional rendering to show the stop button when the stopwatch is running and the start button when it's not.
• 🎨 Introduce basic styling with Tailwind CSS, which can be expanded as the project progresses.
• 🔗 Provide links to resources such as W3Schools for understanding `setInterval` and Tailwind CSS documentation for styling.
• 🎉 Complete a functioning stopwatch app in six steps, demonstrating practical React and CSS skills in under 20 minutes.

Q & A

What is the main purpose of the video script?

The main purpose of the video script is to provide a step-by-step guide on how to create a simple React stopwatch application using Tailwind CSS.

What is the first step mentioned in the script for setting up a React project?

The first step is to use 'create-react-app' to set up the project and name it 'stopwatch'.

What is a React hook and why is 'useState' considered a React hook?

A React hook is a special function that allows you to 'hook into' React state and other features without writing a class. 'useState' is a hook that helps track state or properties between function calls.

What does the 'useState' hook return and how is it used in the script?

The 'useState' hook returns an array with the current state value and a function to update it. In the script, it is used to initialize the 'time' state to zero.

How is time calculated in the stopwatch application?

Time is calculated by dividing the elapsed time in milliseconds by the number of milliseconds per unit of time, using the remainder operator to get the seconds, minutes, and milliseconds.

What are the functionalities provided by the buttons in the stopwatch application?

The buttons provide functionalities for starting, stopping, and resetting the stopwatch.

What is the 'useEffect' hook used for in the script?

The 'useEffect' hook is used to perform side effects in React components, such as fetching data, manually changing the DOM, or setting up timers. In the script, it is used to start and clear the interval for the stopwatch.

Why is 'running' used as a dependency in the 'useEffect' hook?

Using 'running' as a dependency ensures that the effect (starting or clearing the interval) only runs when the 'running' state changes, preventing unnecessary re-renders.

What is conditional rendering and how is it used in the script?

Conditional rendering is a technique in React for rendering different components or elements based on certain conditions. In the script, it is used to show the stop button when the timer is running and the start button when it is not.

How is Tailwind CSS introduced in the script?

Tailwind CSS is introduced as a basic styling tool for the stopwatch application, with a mention of the documentation for further customization.

What is the final outcome of following the script?

The final outcome is a functioning stopwatch application created in React with basic styling using Tailwind CSS, completed in six steps and under 20 minutes.

Outlines

00:00

🛠️ Building a Simple React Stopwatch App

This paragraph outlines the process of creating a basic React application for a stopwatch. The creator skips the introduction to save time and jumps straight into the tutorial. The first step involves setting up the React project using 'create-react-app' and naming it 'one-stopwatch'. The unnecessary elements from the initial setup are removed to streamline the project. The core functionality revolves around using the 'useState' hook to track and update the stopwatch's time. The time calculation is explained, which involves dividing the elapsed time by milliseconds to convert it into a readable format. Buttons for start, stop, and reset are added, with their functionalities tied to the 'running' state. The 'useEffect' hook is introduced to manage side effects like starting and stopping the timer using JavaScript's 'setInterval' and 'clearInterval' methods. A minor issue with the timer continuing to count is resolved by adjusting the dependencies in the 'useEffect' hook.

05:08

🎨 Adding Conditional Rendering and Styling with Tailwind CSS

The second paragraph focuses on enhancing the stopwatch app with conditional rendering and basic styling using Tailwind CSS. The author explains how to implement conditional rendering to display the stop button only when the stopwatch is running, using a ternary operator for this purpose. This approach ensures that the UI is intuitive and only shows relevant controls. The paragraph also provides a brief introduction to Tailwind CSS, including instructions on how to install and apply it to the project. The author mentions the need to restart the application to see the effects of the CSS changes and provides a link to the Tailwind CSS documentation for further customization. The tutorial concludes with a functioning stopwatch that includes all the necessary features and is styled with a minimalistic approach, completed in under 20 minutes.

Keywords

💡React

React is a popular JavaScript library for building user interfaces, particularly for single-page applications. It allows developers to create reusable UI components and manage state effectively. In the video, React is used to create a stopwatch application, demonstrating its utility in handling dynamic content and user interactions.

💡Tailwind CSS

Tailwind CSS is a utility-first CSS framework for rapidly building custom user interfaces. It provides a set of pre-defined classes that can be used to style HTML elements directly in the markup. In the video, Tailwind CSS is introduced as a way to add basic styling to the React stopwatch app, emphasizing its ease of use and flexibility.

💡useState

useState is a React Hook that lets you add state to functional components. State in React refers to a piece of data that can change over time and can trigger a re-render of the component. In the script, useState is used to manage the stopwatch's time and control its start, stop, and reset functionalities.

💡useEffect

useEffect is another React Hook used for performing side effects in function components. Side effects are operations that do not directly affect the rendering of the component, such as data fetching or manually changing the DOM. In the video, useEffect is utilized to handle the stopwatch's timing functionality, starting and stopping the timer based on the component's state.

💡setInterval

setInterval is a JavaScript method used to execute a function repeatedly at fixed time intervals. In the context of the video, setInterval is employed to count the milliseconds for the stopwatch, demonstrating its role in creating time-based functionalities in web applications.

💡conditional rendering

Conditional rendering in React is a technique used to render components based on certain conditions. It allows developers to control what gets displayed in the UI. In the script, conditional rendering is used to show the stop button only when the stopwatch is running, enhancing the user experience by displaying relevant UI elements.

💡state management

State management in React refers to the process of handling and updating the state of a component or application. It is crucial for dynamic applications that require tracking and responding to changes in data. The video demonstrates state management through the use of useState and useEffect to control the stopwatch's behavior.

💡function components

Function components in React are a simpler and more modern way to write components that encapsulate UI logic. They do not have the lifecycle methods and state management capabilities of class components but can be enhanced with hooks. The video uses function components to build the stopwatch, showcasing their simplicity and efficiency.

💡hooks

Hooks in React are functions that let you 'hook into' the React state and lifecycle features from function components. They enable developers to use state and other React features without writing a class. The script mentions useState and useEffect hooks, which are used to manage state and side effects in the stopwatch app.

💡stopwatch

A stopwatch is a timekeeping device used to measure elapsed time. In the video, the main project is a stopwatch application built using React. The script walks through the steps of creating a functional stopwatch, including starting, stopping, and resetting the timer, which is a practical example of using React for real-world applications.

💡re-render

Re-render in React refers to the process of re-executing the render method of a component, which happens when the component's state or props change. In the context of the video, the stopwatch component re-renders to update the displayed time as the state changes, illustrating the dynamic nature of React components.

Highlights

Introduction to creating a simple React stopwatch app with minimal Tailwind CSS styling.

Step-by-step guide starting with setting up a React project using 'create-react-app'.

Explanation of using the useState hook in React to track and update state.

Destructuring the useState return value for current state and state update function.

Calculating time display logic with division and remainder operators for stopwatch functionality.

Adding buttons for start, stop, and reset with corresponding state management.

Utilization of the useEffect hook for side effects like timers in React components.

Setting up setInterval for the stopwatch and clearing it on stop with useEffect.

Conditional rendering to display start or stop button based on the stopwatch state.

Using ternary operators for conditional rendering in React.

Basic introduction to Tailwind CSS for styling the React app.

Instructions on installing and integrating Tailwind CSS into a React project.

Adding basic styling with Tailwind CSS to improve the appearance of the stopwatch.

Link to Tailwind CSS documentation for further customization.

Completion of a functioning stopwatch in React with under 20 minutes of development time.

Practical application of React hooks and conditional rendering for interactive UI elements.

Encouragement for viewers to explore further with Tailwind CSS for advanced styling.

Closing remarks and anticipation for the next tutorial in the series.

Transcripts

this is how I would learn react if I

okay let's cut the Preamble I only have

20 minutes so let's get to the point

the stopwatch everyone seems to do a

countdown timer but I always thought the

stopwatch was more practical so here it

is a super simple react app with the

tiniest bit of Tailwind CSS start stop

reset

Step 1 set up your react projects MPX

create react app and add the name of

your project I want to call this a one

stopwatch

wait for react to work its magic and

then see that it works

remove the stuff you don't need

and let's go

step two

the first thing we need is use State use

state is a react hook now there's a lot

of react specific lingo which I like to

dumb down for myself I think of react

hooks as little react tricks you state

is a little react trick that helps us to

track data or properties in between

function calls when initializing due

State we are destructuring the return

value from you state as shown in the

square brackets

the first value time is our current

state the second value set time is the

function that is used to update our

state

the zero in Brackets is US setting the

initial State as the numeric value of

zero

the more projects you do the more

variations of use that you see so I

won't go into it in detail here

I like to visually see the numbers on

the page so let's do the calculations

now

because this is one big JavaScript file

we can just add in the method here

I don't and will never remember the

calculation by heart but the logic is

like this

the time is calculated by dividing the

time by the number of milliseconds for

each unit of time we need the remainder

operator the percentage sign because

without it if we do 90 000 milliseconds

divided by a thousand we get 90 seconds

that's not much use to us for a

stopwatch like this because we need it

to show one minute 30 seconds so we need

to add the remainder operator to flesh

out the seconds it's 60 for seconds 64

minutes and 104 milliseconds

step 3 let's add the buttons

start stop reset

to add functionality we can just add it

down here when it starts we set running

as true using the U State hook

this state will be remembered and used

for our function later on until the stop

button is clicked and running is set as

false again

on reset we want the time to be zero

simple

step four now this is the real clever

bit of the stopwatch to get it working

we need to use effect hook use effect is

used to perform side effects what does

this mean in react components if the

functional component makes calculations

that don't Target the output value then

these calculations are named side

effects for example data fetching

manually changing the Dom timers Etc

it accepts two arguments callback and

dependencies callback is the function

containing the side effect logic

dependencies is an optional array of

dependencies

the use effect executes callback only if

dependencies have changed between

renderings if you add in the

dependencies

so what's the callback for our stopwatch

if the state is running which means when

the start button is clicked we start

counting the milliseconds using the pure

JavaScript set interval method

if you want to understand more about set

interval check out the w3schools free

resource page link below

if the state is not running which is our

default position and whenever the stop

button is clicked we want to clear the

interval and that stops the timer

finally we want to put running as our

dependency

and to resolve this issue of the timer

keeps counting like this

we just add dot slice minus two

step five conditional rendering now the

icing on the cake would be if the stop

button only shows when the start button

is clicked after all what is the point

of the stop button sitting there at the

beginning when the stopwatch is not

running we can do this easily by using

conditional rendering I like a ternary

operator so let's use that

we'll set the condition first so if the

timer is running we want to see the stop

button we just copy and paste it after

the question mark

if the timer is not running we want to

see the start button

and we copy and paste that button after

the colon

there we go that's the functionality

done

step 6 styling if you are interested in

the basics of Tailwind CSS this is a

super basic intro to adding the most

basic styling we can build it up as we

go along with the other projects

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foreign

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CSS instructions to install it

you may have to stop running the

application and restart again in order

to see the effects of the Tailwind CSS

and then we go straight inside these

tags to start styling

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I'll put the Tailwind CSS documentation

link below if you want to go through it

to add your own colors and things

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thank you

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foreign

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foreign

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and that's it a functioning stopwatch in

six easy steps and under 20 minutes

see you next time