How to render LISTS in React 📃

Summary

This comprehensive tutorial delves into rendering lists in ReactJS, guiding viewers through the complexities of list rendering step by step. It begins by creating a functional component to manage a list, illustrating how to convert an array of strings into list items using JavaScript's map method. The video then explores sorting and filtering arrays, emphasizing the importance of unique keys for list items. It transitions to rendering arrays of objects, showcasing how to display additional properties like calories alongside fruit names. The tutorial also covers making the list component reusable by passing props, and concludes with practical tips on conditional rendering and setting default props and prop types for robust component design.

Takeaways

• 😀 The tutorial focuses on rendering lists in ReactJS, which can be complex but is broken down step by step.
• 📝 A new functional component named 'List' is created to manage the list, demonstrating basic component setup in React.
• 🍎 An array of fruits is used to illustrate rendering arrays, highlighting the conversion of array elements into list items.
• 🔄 The importance of using the 'map' method to transform arrays into list elements is emphasized for dynamic list rendering.
• 🔑 React's requirement for a unique 'key' prop for list items is discussed, ensuring React can efficiently update the DOM.
• 🔍 The tutorial covers sorting arrays with the 'sort' method, including custom sorting functions for alphanumeric order.
• 🏷️ The use of 'filter' method is explained to demonstrate how to display items based on certain criteria, like calorie count.
• 🔀 The process of making the 'List' component reusable by passing different lists as props is detailed, enhancing component flexibility.
• 🎨 Basic CSS styling is applied to the list components to improve the visual presentation of the rendered lists.
• ❗️ Conditional rendering is introduced to handle cases where lists might be empty, ensuring the UI adapts to data changes.
• 🛠️ The tutorial concludes with setting up default props and prop types for the 'List' component to ensure robustness and error checking.

Q & A

What is the main topic of the video?

The main topic of the video is rendering lists in ReactJS, covering various methods and best practices for handling and displaying lists of data.

How does the tutorial start in terms of creating a list component?

The tutorial starts by creating a new function-based component named 'list' in a JSX file within the source folder.

What is the initial data structure used in the tutorial for the list?

Initially, an array of fruit names is used as the data structure for the list.

How is the array of fruits transformed into list items in the component?

The array of fruits is transformed into list items using the built-in JavaScript 'map' method, which returns a new array of list item elements.

Why is it necessary to use a 'key' prop when rendering lists in React?

It is necessary to use a 'key' prop to give each list item a unique identifier, which helps React efficiently update and re-render the list when items are added, removed, or reordered.

How can you sort the list of fruits in the tutorial?

The list of fruits can be sorted using the 'sort' method, which can be applied directly to the array. The tutorial demonstrates sorting both lexicographically by name and numerically by calories.

What is the purpose of converting the array of strings into an array of objects?

Converting the array of strings into an array of objects allows for more complex data structures, enabling the inclusion of additional properties such as 'calories' and makes it easier to manage and display the data in the list.

How does the tutorial handle empty lists or missing data?

The tutorial uses conditional rendering to check if the list has elements before rendering it. If the list is empty or data is missing, it returns null or a default value to ensure the component doesn't try to render undefined data.

What is the benefit of making the list component reusable?

Making the list component reusable allows it to accept different types of lists as props, increasing its flexibility and reducing code duplication across the application.

How does the tutorial enhance the list component with CSS styling?

The tutorial enhances the list component with CSS styling by adding class names and defining styles for list categories and items, including hover effects, to improve the visual presentation of the list.

Why is it recommended to set up prop types in React components?

Setting up prop types is recommended for validating the data types of props passed to a component. It helps catch errors and provides warnings during development, ensuring that components receive the expected data types and improving code reliability.

Outlines

00:00

📝 Introduction to Rendering Lists in React

This segment introduces the topic of rendering lists in ReactJS, emphasizing its complexity. The tutorial begins by creating a new functional component named 'List' within a JSX file. The component is initialized with an array of fruit names, and the video demonstrates what happens when this array is returned within the component. It then shows how to import and use this component in the main 'App' component. The focus is on converting the array of strings into an array of list item elements using the JavaScript 'map' method. The segment concludes with a discussion on rendering unordered lists and the importance of correctly enclosing elements within JSX.

05:01

🔑 Adding Unique Keys and Sorting Lists

The second paragraph delves into the importance of assigning unique keys to list items in React for better performance and state management. It demonstrates how to use the 'key' prop with the fruit names to avoid warnings. The tutorial then transitions into sorting the array of objects by different properties, such as name and calories, using the 'sort' method with custom comparison functions. The video also covers how to display additional information, like calories, alongside each fruit item and how to style the list items using bold tags. The segment ends with a discussion on sorting lists in both ascending and descending orders.

10:01

🍇 Filtering and Reusable List Components

This part of the tutorial focuses on filtering list items based on specific criteria, such as calorie count. It shows how to create arrays for low and high-calorie fruits using the 'filter' method and conditional rendering. The video then shifts to making the 'List' component reusable by passing different arrays as props, including a demonstration of passing an array of vegetables. The segment also covers how to handle empty arrays and the use of default props to ensure that components render even when data is missing. Lastly, it introduces the concept of PropTypes for type checking in React components.

15:03

🎨 Styling Lists with CSS

The fourth paragraph is dedicated to applying CSS styles to the list components. It describes how to add class names to the list items and category headings, and then details the CSS properties used to style these elements, including font size, color, text alignment, and hover effects. The video provides a step-by-step guide on styling the list category with a border, background color, and other visual enhancements. It also covers styling the list items to improve readability and visual appeal.

20:07

✅ Conditional Rendering and PropTypes

The final paragraph discusses conditional rendering to handle cases where lists might be empty. It explains how to use the logical AND operator for concise code when rendering components based on the presence of elements in an array. The tutorial also addresses the importance of setting default props and PropTypes to ensure that components behave correctly even when data is incomplete or incorrect. The segment concludes with a walkthrough of setting up PropTypes for the 'List' component, including defining the expected data types and shapes for the props.

Keywords

💡ReactJS

ReactJS, often simply referred to as React, is a popular open-source JavaScript library primarily used for building user interfaces, especially for single-page applications. It is maintained by Facebook and a community of individual developers and companies. In the video, ReactJS is the main framework discussed, with the tutorial focusing on rendering lists within React components, which is a fundamental aspect of managing dynamic content in web applications.

💡Component

In React, a component is a fundamental building block used to create a reusable piece of HTML structure, often encapsulating both data and behavior. The video script describes the creation of a new functional component named 'List', which is used to render lists of data. Components can be class-based or function-based, and in this case, a function-based component is created and exported for use elsewhere in the application.

💡Array

An array in JavaScript, and thus in React, is a global object that is used to store multiple values in a single variable. In the script, arrays are used to hold lists of fruits and vegetables, which are then rendered within the 'List' component. Arrays are manipulated using methods like 'map', 'filter', and 'sort' to transform and display the data in various ways within the React component.

💡Map Method

The map method in JavaScript creates a new array with the results of calling a provided function on every element in the calling array. In the video, the map method is used to transform an array of fruit names into an array of list item elements, which are then rendered within the 'List' component. This is a common pattern in React for rendering collections of data.

💡List Item Elements

List item elements, such as 'li' for unordered list items or 'ol' for ordered list items, are HTML elements used to represent items in a list. In the context of the video, these elements are dynamically created from an array of data using the 'map' method and are then returned by the 'List' component to display the data in a list format on the webpage.

💡Props

Props in React are a way to pass data from a parent component to a child component. The video script describes how an array of fruits and a category string are passed as props to the 'List' component. Props allow for making components reusable and customizable, as they can receive different data to render different content.

💡Key Prop

In React, each child in a list should have a unique 'key' prop. The key helps React identify which items have changed, are added, or are removed. In the video, the tutorial initially encounters a warning about the need for a unique key prop, which is then resolved by assigning a unique 'ID' to each object in the array. This is crucial for performance optimization and accurate rendering of lists in React.

💡Sort Method

The sort method in JavaScript sorts the array in place and returns the sorted array. In the video, the sort method is used on arrays of objects to order the list items by properties like 'name' or 'calories'. The tutorial demonstrates how to write custom sorting functions to handle both ascending and descending orders, which is essential for presenting data in a user-friendly manner.

💡Filter Method

The filter method in JavaScript creates a new array with all elements that pass the test implemented by the provided function. In the video, the filter method is used to create subsets of the original array, such as filtering out fruits with low or high calorie counts. This method is showcased as a way to dynamically alter the data presented in the 'List' component based on specific criteria.

💡CSS Styling

CSS (Cascading Style Sheets) is used to style the appearance of web content. In the video, CSS is applied to the 'List' component to enhance the visual presentation of the list items and category headings. The tutorial covers how to add classes to elements and define styles in a CSS stylesheet, which is an important aspect of web development for creating a polished user interface.

💡Prop Types

Prop types in React are used to validate the props passed to a component, ensuring that they match the expected data types. The video script includes a section on setting up prop types for the 'List' component, which helps catch errors and enforces best practices. This is demonstrated as a way to ensure that the data passed to the component is of the correct type, preventing potential bugs and improving code maintainability.

Highlights

Introduction to rendering lists in ReactJS with a step-by-step tutorial.

Creating a new functional component named 'List' in a JSX file.

Exporting the 'List' component for use in other parts of the application.

Using an array of fruits to demonstrate rendering lists in React.

Returning an array within a React component and the need for importing it.

Converting an array of strings into an array of list item elements using the map method.

Using arrow functions for cleaner and more concise code.

Creating an unordered list with JavaScript embedded within JSX.

Sorting an array of strings lexicographically using the sort method.

Transforming an array of strings into an array of objects with additional properties.

Adding a unique key prop to each list item as recommended by React.

Using a unique ID as a key for list items to avoid naming conflicts.

Displaying additional data, such as calories, alongside each list item.

Sorting the array of objects by properties like name or calories.

Filtering objects based on criteria, such as calories being greater than 100.

Making the 'List' component reusable by passing different lists as props.

Applying CSS styling to list components for better visual presentation.

Using conditional rendering to display lists only if they contain elements.

Setting up default props to handle missing or undefined properties.

Establishing prop types for better debugging and data type validation.

Conclusion and encouragement for further study and practice with rendering lists in React.

Transcripts

hey everybody I have a huge video for

you today today we're going to talk

about rendering lists in reactjs this

can be pretty complex we'll go through

it step by step what we'll do in this

tutorial is create a new component to

hold our list let's go to our source

folder create a new file I'll name this

component list this will be a jsx file

to finish creating this component this

will be a function based

component with the name of list then be

sure to export it export default

list we'll start with something very

simple we'll create an array of fruit

this will be const fruits equals think

of some fruit for me I'll pick an

apple

orange

banana coconut and a

pineapple let me show you what would

happen if we were to return our array

within our list component we will

return our array of fruits but we will

need to import it going back to the app

component we will import our list

component import list from a

location SL list.

jsx we need a return statement to be

sure you have one we will return a list

component and here is our list let me

zoom

in it's all one big string Apple orange

banana coconut pineapple heading back to

our list component we need to convert

our array of strings into an array of

list item elements we can use the

built-in map method to do that we'll

create a new array of list items the map

method is going to return a new array

after running it through a function

function const list items equals take

our original array of fruits use the

built-in map method then we'll either

pass in a callback a function expression

or an arrow function we'll use Arrow

functions because I like Arrow functions

for every fruit in fruits Arrow meaning

do this we'll create a new list item

element that has the text of our fruit

the array item we're not going to return

our fruits array we're going to return

an unordered

list we're going to insert some

JavaScript with curly braces we'll

include our list items it's an array of

list items and here's our array whoops

but I forgot to enclose fruit with curly

braces my mistake they are much better

better or if you prefer we can turn this

unordered list into an ordered list with

a pair of O

tags

o there they're all numbered that's how

to render a simple array if you're

working with an array of strings and

you'd like to sort this array beforehand

you can use the sort

method fruits. sort the sort method will

sort an array in place however this

doesn't work with numbers because we're

sorting

lexicographically we would treat numbers

and symbols as characters more on that

later let's go over example two we'll

convert our array of strings into an

array of objects each object will have a

name property and calories calories per

serving so let's enclose all of our

elements within a set of curly braces to

make them

objects I'm going to place each of these

objects on a new line just so that I can

read it more

easily each of these objects will have a

name property the name property will be

set to the original string for our array

the first object will have a name of

Apple let's add calories too calories

per

serving I did a quick Google search of

some of the calories per serving for

these fruits I don't know how accurate

these are but they seemed right our

first object has a name of Apple

calories is set to 95

name orange

calories

45 name

banana calories

105 name

coconut coconut

calories

159 name pineapp

example

calories

37 all right we now have an array of

objects there's a few changes we're

going to make if I run this again our

list is in rendering I need to display

the name property of each fruit fruit.

name

property we have one issue behind the

scenes I'm going to right click go to

inspect then go to

console

warning each child in a list should have

a unique key prop react wants us to

assign a key to each list item each key

should be unique in my array of objects

each fruit has a unique name I could use

that we will set the key attribute to

equal include some

JavaScript fruit. name that warning

should go

away

which it did if there's a possibility

that two objects can share the same name

you'll want to use some sort of unique

ID in a real world scenario if you're

pulling data from a database each row of

data is going to have some sort of

unique ID so we're going to mimic that

let's add a new property for an

ID ID will be one for Apple these will

be in ascending order orange will have

an ID of two banana is

three coconut is four pineapple is

five we'll set the key to be each

ID this would be much better than using

the name you can have a naming conflict

if two objects share the same name like

if these were people you could have two

people named Bob that warning should be

gone which it is react would like a

unique key for each item just so it can

more easily keep track of items being

inserted and removed along with each

element I'm going to display the

calories next to each

element so we'll make a few changes I'm

going to put these HTML elements on a

new line for

readability after the fruit's name I'm

going to add a

colon a non-breaking space character and

Pand nbsp for space oh then not a

semicolon forgot about

that then we'll ins some

JavaScript fruit. calories for the

calories of each

fruit I'll make it bold I'll enclose our

calories with a pair of bold tags which

is just

B now we're going to sort the items in

our list we'll do that before the map

method I'm going to sort our array of

objects by their name property we'll

take fruits

use the sort method the sort method will

sort an array in place we'll write a

custom sorting function we have two

parameters A and B A for the first item

B for the second then we iterate over

the entire

array we need an arrow meaning do

something to lexicographically sort

string properties within an array we can

use the following method we'll take the

name property of a use the built-in Loc

local or local some people say compare

method I misspelled

that yeah I can't spell

compare to b.n name that should sort our

array of objects by their name property

for reverse order let me turn this line

into a comment this is

alphabetical for reverse alphabetical

order we just have to replace a with B

and B with a there pineapple orange

coconut banana apple with apple being at

the

bottom let's sort by

calories fruits. sort this one's easier

again we have our parameters a comma

B Arrow the calories of a a.

calories minus b.

calories that one's easy we have

pineapple at the top followed by orange

apple banana

coconut this is in numeric

order for reverse numeric

order reverse

numeric or descending you could say the

calories of B minus the calories of a

now we have coconut at the top with

pineapple at the bottom with the least

amount of

calories in this next section I'm going

to demonstrate to you how we can filter

objects by a certain criteria we'll

filter anything that's greater than 100

calories we'll create a new array of

fruit that has low

calories we'll create a new array const

low cal

fruit equals take our original array of

fruits use the built-in filter

method we'll have one parameter of fruit

examine each fruit in our array of

fruits and Arrow then a condition here's

the

criteria check the calories property of

our

fruit if it's less than 100 filter it

and add it to a new array instead of

displaying our array of fruits let's

display our new array of low calorie

fruit oh that should be plural low cal

fruits when we create our array of list

items replace fruits with low cal fruits

and any instance of fruit with local

fruit

singular so we have three instances of

fruit let's replace

those let me clean this up a

little feel free to pause the video if

you need to write this

down we have three fruits that are low

calories the calories is less than 100

let's find any high calorie

fruits we can just copy this line of

code paste it but change the condition

examine the calories of each fruit

filter it out if the calories are

greater than or equal to

100 the name of this array will be high

Cal

fruits replace low calow fruits with

high Cal

fruits replace low cal fruit with high

Cal fruit

singular and do that for the other

instances as

well there we are we have two fruits

that are high in calories bananas and

coconuts that is US using the filter

method to filter out list items let's

replace High Cal fruits with fruits high

Cal fruit with fruit to display our

original

array for the next part of this lesson

we're going to transform this list

component so it's reusable with

different lists currently the way that

we set this up is that each list

component that we create has its own

list of fruit so we're going to make

some

changes let's cut our list of

fruits going to the parent component of

app we'll paste our list of fruits then

pass it as props to our list

component with our list component we

will have a key of items equals insert

some JavaScript our list of fruits let's

also add a category

key category equals for my category

let's say fruits eventually we'll add an

H3 heading we're now going to send all

of this data to the list component but

we have to set up props within the list

function we have a parameter of

props we'll access the items of props to

get our fruit

we'll create const item list equals not

to be confused with list items list

items is what we get after we map

it item list equals props do items and

remember that items is our fruits

array replace fruits with item

list replace fruit with

item do that here here and

here there's our list

again if you're going to sort or use the

filter method be sure it's item list not

fruits because now list is a reusable

component I'll add our category two

that's stored within props const

category equals props do

category currently we're returning a

single ordered list I'll also include an

H3 element

include some JavaScript we need curly

braces add our

category however with our return

statement we can only return a single

element or many elements that are

wrapped within a fragment let's create a

fragment that will enclose all of our

markup there we

are going back to our app component

let's create a new list just to make

sure that our list component is

reusable let's copy our array of

fruits paste

it we'll create an array of

vegetables the IDS will be 6 7 8 9

10 the name of my first item will be

potatoes calorie 110 per

serving

celery calories will be

15 carrots calories

25 corn calories

63

broccoli calories

50 now we should be able to create a new

list

component within our return turn

statement we're going to need a fragment

again we'll return a second list item

component the items will be vegetables

the category will be a string of

vegetables boom there we go here's our

second list

component so our list component is now

reusable we can pass in many different

types of lists to make this look better

let's apply some CSS styling we'll have

to set a class name

first our H3 element will have a class

name equal

to list-

category our ordered list will have a

class name of list

items all right going to our CSS

stylesheet index.css let's work on our

list category

first use dot to select a class list

category I'm just going to run through

these real quick I'm going to make sure

I'm zoomed in to 100 because I was

zoomed in

beforehand font size 2.5

em font weight will be

bold pick a

color I'm going to stick with hsl values

I'll set the lightness to be

20% I'll add a little bit of margin on

the

bottom 10

pixels text align

Center I'll add a

border three pixel

solid I'll add a border radius to round

the

corners

and a background

color pick a color again I'll use

hsl this one I pre-picked already

185

100%

50% that's not a bad looking color pick

whatever color you would like let's work

on our list item

elements we need to select the class of

list

items do list items select each list

item within this

class I'll increase the font size to be

2

em I'll remove the list style but you

don't have

to list style will be

none pick a color again I'm using hsl

values I'll set the lightness to be

25% text align

Center and margin will be

zero all right now when I hover over one

of these list items I'll apply a hover

effect take our class list items take

each list item access the hover sudo

class I'll change the brightness the

color will be something a little bit

brighter I'll set the lightness to be

45% and then the cursor will be a

pointer yeah not bad that's how we can

apply some CSS styling to list

components all right heading back to our

app component what if we have an empty

list for example with our fruits I'm

going to cut

it we can use conditional rendering to

render our list only if there's elements

let's put put those back we're going to

write some JavaScript we need some curly

braces let's take our array of fruits

access the length

property is it greater than

zero question mark if it is we'll return

our list

component colon if it's false we can

return null let's do that with our

vegetables

too take our array of vegetables

AIS the length property is a greater

than zero tary operator if it is return

our list

component if not we can return

null if one of these lists doesn't have

any elements we won't render that

component there is a short hand to the

tary operator we don't need to write or

else return null what we'll use instead

of the trary operator is the and logical

operator we can effectively Short

Circuit the first

expression then we don't need colon null

it's a little less

code our list component will always be

true because it

exists however the first expression

might not be so if this condition is

false we don't render this if it is true

we will render this let's try that again

let's remove these

elements we don't display the fruits

list

component and we will not display the

vegetable list

component this is known as short

circuiting one thing to consider what if

our category is missing let's remove our

category from

fruits well I would like to add some

sort of placeholder here or what if one

of these arrays was

missing well nothing displays not even

vegetables we should add some default

props in case one of these properties is

missing so going back to our list

component before we export it let's set

up some default props take our component

name list. default props equals within a

set of curly braces let's set our

category category

property to be category as a placeholder

if for some reason these components

don't have a

category we'll add a placeholder of

category which at least looks better if

we're missing an array that's a bigger

problem let me go to inspect then

console we're trying to map something

that's undefined we have no array to

work with so nothing is rendering so as

a backup Within default props let's set

our items to be an empty

array items will be an empty

array if one of these arrays was missing

for some

reason at least the category is

displayed as well as the subsequent

components at least something will

display okay then lastly as good

practice if we're accepting props we

should set up prop types I'll walk you

through it if you're just joining us

with prop types if the incorrect data

type is passed into props when we debug

it'll give us a

warning to use prop types we have to

import it at the top of our list

component we will

import prop

types

from prop

types take our component of

list

list. prop

types

equals set of curly braces for our

category this will be a

string category colon

space prop types do

string add a comma for another line okay

this is where it's going to get tricky

we have an array of

objects we'll access the items

property items colon

space to types I'm going to move down a

little

bit dot we have an

array

array of we have an array of

objects prop

types do shape method we have to define

the shape of each object each object is

going to have its own data types we have

a number string then

number we're defining an object we need

a set of curly

braces ID

colon prop types.

number comma for another

property I'll put the next one on a new

line for

readability we have a name property

which will be a string prop types.

string then

calories

prop types.

number and that's

it let's head back to our app

component our prop types should raise a

warning if some of our data is of the

wrong data type for example let's say

that calories is now the string Apple

maybe somebody mistyped it

twice you can see that right here it

changed let's go to

inspect

console

and here's our warning because we have

prop type set up invalid prop items

index zero calories of type

string if we didn't have prop type setup

we wouldn't receive that warning this

may go unnoticed it is good practice if

you're accepting props to also set up

prop types it's a little more

complicated if you have an array of

objects but here are the steps all right

everybody I know this was a massive

topic thank you all for watching feel

free to take some time to study and work

with this before moving on to the next

topic if you would like we did Cover a

lot of material and well those are

various ways in which we can render

lists and

react