01. Stopwatch/Count-Up Timer || Learn React Through Mini Projects
Summary
TLDRThis 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
🛠️ 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.
🎨 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.
Mindmap
Keywords
💡React
💡Tailwind CSS
💡useState
💡useEffect
💡setInterval
💡conditional rendering
💡state management
💡function components
💡hooks
💡stopwatch
💡re-render
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
[Music]
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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
[Music]
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thank you
[Music]
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foreign
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foreign
[Music]
[Music]
and that's it a functioning stopwatch in
six easy steps and under 20 minutes
see you next time
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