React useState() hook introduction 🎣
Summary
TLDRIn this video, the presenter introduces React Hooks, a feature that enables functional components to use React features without writing class components, introduced in React 16.8. The focus is on the useState hook, which allows for stateful variables and their update functions. The tutorial walks through creating a reactive counter program, demonstrating how to use useState to manage state changes that trigger re-renders in the virtual DOM. The video also covers creating stateful variables for name, age, and Boolean values, and concludes with styling the counter with CSS.
Takeaways
- 📌 React hooks were introduced in version 16.8, allowing functional components to use state and other React features without writing class components.
- 🔑 The `useState` hook is fundamental for creating stateful variables and their setter functions within functional components.
- 💡 Using `useState` provides a way to update state and trigger re-renders in the React virtual DOM, unlike regular variables which do not cause re-renders.
- 🛠️ The `useState` hook returns an array with two elements: the current state value and a function to update it.
- 📝 When using `useState`, you can optionally pass an initial state value; if not provided, it defaults to `null`.
- 🔄 The script demonstrates creating a counter program using `useState` to manage incrementing, decrementing, and resetting a count.
- 🎨 Conditional rendering is shown by toggling a Boolean state to display 'yes' or 'no' based on its value.
- 👩💻 The video includes a step-by-step guide on setting up a new React component and using hooks within it.
- 🌐 The script covers the necessity of importing React and destructuring `useState` from it to use within functional components.
- 🖌️ CSS styling is applied to enhance the visual presentation of the counter component, demonstrating the integration of React functionality with styling.
Q & A
What is a React Hook?
-A React Hook is a special function that allows functional components to use React features without writing class components. It was introduced in React version 16.8.
Why were React Hooks introduced?
-React Hooks were introduced to allow developers to use state and other React features in functional components without the need to write class components.
What is the most widely used React Hook?
-The most widely used React Hook is `useState`, which allows the creation of a stateful variable and a setter function to update its value.
How does the `useState` hook work?
-The `useState` hook returns an array with two elements: a stateful variable and a setter function. The setter function is used to update the state, which triggers a re-render of the component.
Can you provide an example of how to use the `useState` hook?
-To use `useState`, you import it from React and call it within a functional component. For example, `const [name, setName] = useState('');` creates a stateful variable `name` and a setter function `setName`.
What is the purpose of the setter function returned by `useState`?
-The setter function returned by `useState` is used to update the stateful variable. When called with a new value, it updates the state and causes the component to re-render with the new state.
How can you set an initial state with `useState`?
-You can set an initial state by passing it as an argument to the `useState` hook. For example, `const [age, setAge] = useState(0);` sets the initial state of `age` to 0.
What is the difference between a normal variable and a stateful variable in React?
-A normal variable does not trigger a re-render when updated, whereas a stateful variable created with `useState` does trigger a re-render, allowing the UI to reflect the updated state.
Can you explain the concept of conditional rendering in the context of the `useState` hook?
-Conditional rendering with `useState` can be achieved using logical operators to determine what to display based on the state. For example, `isEmployed ? 'Yes' : 'No'` will display 'Yes' if `isEmployed` is true, and 'No' otherwise.
How do you create a counter program using React Hooks?
-To create a counter program, you use the `useState` hook to manage the count state and provide functions to increment, decrement, and reset the count. These functions are then used as event handlers for buttons in the component's JSX.
What are some other React Hooks mentioned in the script?
-Other React Hooks mentioned in the script include `useEffect`, `useContext`, `useReducer`, and `useCallback`, each serving different purposes such as managing side effects, providing context, and optimizing performance.
Outlines
🛠️ Introduction to React Hooks
The paragraph introduces the concept of React Hooks, explaining that they are special functions allowing functional components to utilize React features without writing class components. This was introduced in React version 16.8. The paragraph also discusses the 'useState' hook, which is the most commonly used. It allows for the creation of a stateful variable and a setter function to update its value. The video aims to create a reactive counter program using the useState hook by the end.
🎯 Creating a Stateful Variable with useState
This section provides a step-by-step guide on using the 'useState' hook to create a stateful variable and a setter function in a functional component. It explains the process of importing the hook, using array destructuring to extract the stateful variable and setter function, and updating the stateful variable with the setter function. The paragraph also includes a practical example where a 'name' variable is updated using a button click, demonstrating the re-rendering of the virtual DOM when the stateful variable is changed.
🔢 Incrementing and Toggling State with useState
The paragraph delves into creating additional stateful variables such as 'age' and a Boolean 'isEmployed'. It explains how to increment the 'age' variable by one or more with each button click and toggle the 'isEmployed' Boolean value between true and false. The video script includes the code for creating these variables, updating them, and rendering the updated values in the UI. It also touches on conditional rendering using the ternary operator for displaying the 'isEmployed' status.
🔄 Building a Counter Program with useState
The final paragraph focuses on building a counter program using the 'useState' hook. It outlines the creation of a 'count' stateful variable with initial value zero and functions to increment, decrement, and reset the counter. The paragraph includes the JSX code for rendering the counter, buttons for controlling the counter, and a brief mention of styling the counter component with CSS. The video script concludes with a demonstration of the counter functionality and a summary of the 'useState' hook's capabilities.
Mindmap
Keywords
💡React Hooks
💡useState
💡Functional Components
💡Class Components
💡Virtual DOM
💡Array Destructuring
💡Stateful Variable
💡Setter Function
💡Conditional Rendering
💡CSS Styling
Highlights
Introduction to the useState React hook and its role in functional components.
Explanation of React hooks as a feature introduced in React version 16.8.
Overview of various React hooks including useState, useEffect, useContext, useReducer, useCallback, and more.
Detailed explanation of useState hook for creating stateful variables and setter functions.
Demonstration of how to use useState hook in a functional component.
Importing the useState hook from the React library using object destructuring.
Creating a stateful variable and setter function using array destructuring.
Example of updating the stateful variable using its setter function to trigger a rerender.
Explanation of the difference between stateful variables and normal variables in React.
Creating an initial state for the useState hook.
Incrementing a stateful variable using a function and the setter.
Creating a Boolean stateful variable and toggling its value with a button click.
Conditional rendering based on the stateful variable's value using the ternary operator.
Building a counter program using the useState hook to manage count state.
Creating functions to increment, decrement, and reset the counter state.
Styling the counter program with CSS for better user interface.
Final demonstration of the fully functional counter program with styled buttons and display.
Summary of the useState hook's capabilities and its importance in React functional components.
Transcripts
hey what's going on everybody in today's
video I'm going to explain the usate
react hook and near the end of this
video we're going to create a reactive
counter program so sit back relax and
enjoy the show I haven't explained what
react hooks are yet a react Hook is a
special function that allows functional
components to use react features without
writing class components this was a
change made in react version 16.8
basically we no longer need to write
class components we can write function
based components that use rea hooks to
use react features there are many react
hooks if a function begins with use it's
probably a react hook use State use
effect use context use reducer use
callback and more use state is the most
widely used use state is a react hook
that allows the creation of a stateful
variable and a Setter function to update
its value in the virtual Dom basically
by using the UST State hook we can
create not just a variable but a
stateful variable when you update this
variable that change will be reflected
in the virtual Dom normal variables
don't when you use the UST State hook
you're given a variable and a Setter
function specifically for that variable
so what we'll do in this example is
create a new component going to our
source folder we're going to create a
new file we'll name this component my
component we use react hooks in function
based components so make sure you're not
writing a class
component with this component we will
export it export default my component
then be sure to import this because I'm
probably going to forget if we don't do
it now so we will import my
component from its location
do/ my component and this is a jsx file
let's return one my
component and we are ready to begin in
order to use a react hook we need to
import it it at the top of this
component we will import the react
Library however we don't need the entire
react Library we can use object
destructuring to extract individual
variables or functions I would just like
the UST State function we don't need the
entire react library from its location
react we now have access to this use
State function using the use State
function we'll create a stateful
variable and a set function to update
that variable so let's declare const
we're going to use a set of straight
brackets for array
destructuring equals use State function
the use State function returns an array
with two elements a variable and a
Setter function we're going to use array
destructuring to destructure these two
elements we'll create a stateful
variable for name then we're given a
Setter function specifically for this
variable a common naming convention is
to typee set then the variable name with
camel case naming convention and that's
it if we ever need to change the value
of the stateful variable we have to do
so with this Setter it's a function at
the bottom we're going to
return a
development within this development
we'll create a paragraph element and a
button we'll begin with a paragraph
element that has text of name
and I'm going to zoom in a little bit I
will insert some JavaScript using curly
braces let's display our name following
our paragraph element let's include a
button the button will have an onclick
attribute equal to a JavaScript function
so we need a set of curly braces to
embed that let's create a function to
update name for the text of the button
let's say set name
name all right now we just need to
declare this function I'll use an arrow
function const update name equals Arrow
function so what would we like to do
okay let's attempt to set our name equal
to type your name or some other name I'm
just going to type in
SpongeBob if I click on this button we
should update our name right well that
doesn't appear
work so if I were to
console.log my name
variable then attempt to update it using
this button if I were to go to my
console hold on I'm going to use let so
we can update it if I attempt to change
this name of the
variable it does so within our
console but it doesn't update in react
the virtual Dom is still displaying the
previous state so if I would like to
display display any changes I will want
to use that Setter instead of setting
our name equal to a new value I'm going
to change this back to be a
constant we will use the setter function
and pass in a new value so let me type
in a new
value and that should work we have
updated our name when you use the setter
function of a stateful variable it will
trigger a rerender of the virtual Dom
normal variables don't that's why the US
state Hook is useful we can create a
stateful variable when the stateful
variable gets updated with its Setter
function it triggers a render of the
virtual Dom with the UST State function
you can pass in an initial state
currently we're not passing in anything
for the initial State I will set this to
be
guested when I refresh everything and
start over the initial state is guessed
whatever value you pass in to the UST
State hook then I can set my name again
to something else now we're going going
to create an age variable and increment
it const we're going to use array to
structuring we need a stateful variable
like age and a Setter function for that
age set age equals use
state if you would like an initial value
you can place that within the UST State
function I'll set the initial value of
age to be
zero I'm going to copy this paragraph
and this button
change name to be
age we'll create a function to increment
age the text on the button will
be increment
age now we just need this
function
const increment age I'll use an arrow
function to increment our age we will
use the set age
function let's take our age +
one so our initial value for our age is
zero but every time I click on the
button we will update the value of that
variable so every time I click the
button we're increasing our age by
one or even a different number this time
I'll increase our age by two on each
button click so we start at zero then
we'll increment by two 2 4 6 8 10
now this time we'll create a Boolean
variable and toggle it between being
true and false using the usate hook we
will create const is
employed the setter function will be set
is
employed equals the use State
hook I would like an initial value of
false let's create a paragraph element
and a button
I will set the text of the paragraph to
be is
employed instead of displaying a Boolean
directly let's use the tary operator for
conditional rendering is employed if
that is true we'll display yes otherwise
no when we click on the button let's
create a function
to
toggle toggle employed
status that's kind of a Long Function
name all right let's create a function
const toggle employed status equals an
arrow
function we will use the setter function
set is employed pass in a new value
let's switch this value from being false
to true and true to false every time we
click the button since this is a Boolean
we can use the not logical operator to
reverse it so let's say not is
employed and let's see if this works is
employed no oh let's change the text on
the button
too toggle
status there we go all right when we
click on the button we can toggle this
Boolean from being true to false and
false to true and this should happen
every time I click the
button as a project what we're going to
do now is create a counter program so
let's close out of my
component we'll create a new component
for a counter component counter.
jsx this will be a function base
component
function
counter then be sure to export it export
default
counter going back to our app component
we will import our counter component
from its
location counter. jsx then we will
include one counter component and that's
it in order for us to use the use State
hook we have to import it from the react
Library import react we'll use object
destructuring just to get the US state
hook and nothing else from its location
of
react all we need is one variable a
counter let's say const we'll use array
destructuring create a stateful variable
of count and a Setter function for that
count set count equals the use State
hook would we like an initial value for
count we would like the initial value to
be
zero we'll create a few functions to
increment decrement and reset the
counter const
increment equals I'll use an arrow
function to up update the count to
increment it we will use the set count
function the value we pass in is Count +
one then let's do this for
decrement const decrement count minus
one then
reset const reset for set count we'll
pass in zero to reset the
count now we're going to return some
elements we'll also style this with CSS
let's begin with the div
element I'm going scroll down a little
bit my div element will have a class
name equal to
counter-
container I will create a paragraph
element with a class
name equal to count
display to display the
number for the text of the paragraph I
will insert some JavaScript and display
our count
variable we'll create three buttons for
the first we'll create a button element
this button will have a class
name of
counter-
button the onclick attribute will be set
equal to a JavaScript function this
first button will be the decrement
button for the unclick attribute we will
set this equal to the decrement function
for the text on the button we'll say
decrement and there's our first button
so let's copy this button paste it the
second button will be for reset the text
will be
reset then the third button will be
increment onclick will be the increment
function
the text will be
increment all right and that's all that
we need let's check it for functionality
to be sure that everything works we can
increment this number we can decrement
it and we can reset
it so for the icing on the cake let's
style it with
CSS going to our index CSS stylesheet
we'll apply the following CSS let's
select our counter
container do counter container I will
text align
Center change the font
family I will pick a s serif font of
Ariel with a backup of s
serif next we'll select the count
display select the class of count
display that would be this number will
increase the font size to something
massive like 10 em RM works too okay
that's a little too big but I am zoomed
in actually you know what that's perfect
I will set the margin top to be zero to
close this Gap and I will set the margin
on the bottom to be 50
pixels then let's work on the counter
buttons
next select the class of counter button
I will set the width to be 150 pixels
the height to be 50
pixels the font
size to be 1.5
em I will set the font weight to be
bold set the margin to
be 0 pixels by 5
pixels this would be for the left and
right of the
buttons change the background
color pick a color that you
like I'm going to use hsl values
though that's pretty good I will set the
color of the font to be
white remove the
border border
none set the Border radius to around the
corners five
pixels
and change our cursor to be a pointer if
we hover over the button when we hover
over the button I'm going to change the
background color of the button so with
the counter button class with the
counter button class we will select the
hover sudo class we'll take our
background color decrease the lightness
to be 10%
darker there we
are and that is all the CSS styling that
we need we have our counter program we
can increment the counter we can
decrement it and we can reset
it all right everybody so that is the
use State react hook it allows the
creation of a stateful variable and a
Setter function to update its value in
the virtual Dom when you include the UST
State hook you're given an array of two
elements we use array destructuring to
create a stateful variable and a Setter
function to update that variable and
well everybody that is the UST State
hook in react
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