ReactJS Tutorial - 25 - Fragments
Summary
TLDRThis video tutorial delves into React Fragments, a feature that allows developers to group child elements without adding extra nodes to the DOM. The instructor begins by creating a 'Fragment Demo' component, illustrating how fragments solve the issue of JSX requiring a single parent element for multiple children. They demonstrate the use of fragments in a table example, showing how fragments can eliminate unwanted div tags and resolve console warnings about improper DOM nesting. The video also covers the key attribute in fragments for rendering lists and the shorthand syntax for fragments, highlighting its limitation of not allowing key attributes. The tutorial is a practical guide for React developers looking to streamline their JSX structures.
Takeaways
- 📕 React Fragments are used to group a list of children elements without adding extra nodes to the DOM.
- 📝 In React, when returning multiple elements, they must be enclosed within a single parent element.
- 📝 The error message 'JSX expressions must have one parent element' indicates that JSX elements need to be wrapped in an enclosing tag.
- 📝 React Fragments can prevent the addition of unnecessary DOM nodes by replacing enclosing tags like div.
- 📝 The DOM tree can be cleaned up by using React Fragments, as they do not add extra nodes like divs.
- 📝 React Fragments can be used in scenarios where multiple elements are returned, such as in table rows with multiple cells.
- 📝 Console warnings like 'validate DOM nesting TD cannot appear as a child of the div' can be resolved by using React Fragments.
- 📝 The key attribute can be passed to React Fragments when rendering lists of items, which is useful for identifying elements in a collection.
- 📝 Currently, the key attribute is the only attribute that can be passed to a React Fragment, with potential for more attributes to be supported in the future.
- 📝 There is a shorthand syntax for React Fragments using empty opening and closing tags, but this does not support passing the key attribute.
Q & A
What is the primary purpose of React Fragments?
-React Fragments allow you to group a list of children elements without adding extra nodes to the DOM.
How do you create a React Fragment?
-You can create a React Fragment by using either `<React.Fragment>` or the shorthand syntax `<>...</>`.
What is the issue when returning multiple JSX elements without using a Fragment?
-If you return multiple JSX elements without using a Fragment, React will throw an error stating that JSX expressions must have one parent element.
Why is it important to avoid extra nodes in the DOM?
-Avoiding extra nodes in the DOM is important for performance optimization and to prevent unnecessary nesting that can lead to styling and layout issues.
Can you pass the 'key' attribute to a React Fragment?
-Yes, you can pass the 'key' attribute to a React Fragment, which is especially useful when rendering lists of items.
What is the limitation of using the shorthand syntax for React Fragments?
-The limitation of using the shorthand syntax for React Fragments is that you cannot pass in the 'key' attribute.
How do you fix the warning 'validateDOMNesting TD cannot appear as a child of a div'?
-You can fix this warning by replacing the enclosing `div` tag with a `<React.Fragment>` to prevent the extra node from being added to the DOM.
What is the correct way to include a React Fragment in a component?
-You include a React Fragment in a component by replacing the enclosing parent tag (like `div`) with `<React.Fragment>` or `<>...</>`.
What is the significance of the 'key' attribute in the context of React Fragments?
-The 'key' attribute is significant in React Fragments when rendering lists as it helps React identify which items have changed, are added, or are removed, which is crucial for performance optimization.
Can React Fragments accept attributes other than 'key'?
-As of the knowledge cutoff in 2023, React Fragments can only accept the 'key' attribute. However, React plans to allow additional attributes in the future.
What is the benefit of using React Fragments over a simple enclosing tag like 'div'?
-Using React Fragments over a simple enclosing tag like 'div' prevents the addition of unnecessary DOM elements, which can lead to cleaner HTML structure, better performance, and fewer potential layout issues.
Outlines
🛠️ Introduction to React Fragments
This paragraph introduces React fragments, explaining their purpose and functionality. A React fragment allows developers to group a list of child elements without adding extra nodes to the Document Object Model (DOM). The tutorial begins by creating a new file named 'fragment demo.js' and using a React snippet to create a functional component. The component is then added to the 'app' component. The instructor then demonstrates how to convert text into a heading using an 'h1' tag and add a description using a 'p' tag. However, this results in a JSX error because JSX expressions must have one parent element. To fix this, an enclosing 'div' tag is added. Upon saving the changes, the application works, but an extra 'div' tag is added to the DOM. To avoid this, React fragments are used in place of the 'div' tag, which prevents the extra node from being added to the DOM. The paragraph concludes with another example where fragments are more appropriate, such as creating a table with columns in separate components.
📚 Advanced Usage of React Fragments
The second paragraph delves into more advanced usage of React fragments, focusing on DOM nesting validation and the shorthand syntax for fragments. The instructor creates two new files, 'table.js' and 'columns.js', to demonstrate how to create a table with columns. Initially, an enclosing 'div' tag is used to return multiple elements, which leads to console warnings about incorrect DOM nesting. The 'div' tag is then replaced with a React fragment to resolve these warnings. The paragraph also discusses the ability of fragments to accept the 'key' attribute when rendering lists, which is crucial for performance optimization in React. The instructor provides an example of how to use fragments with the 'key' attribute and mentions that React plans to support additional attributes for fragments in the future. The paragraph concludes with a discussion of the shorthand syntax for fragments, which allows for the grouping of elements without adding extra nodes to the DOM, but notes that the shorthand syntax does not support the 'key' attribute.
Mindmap
Keywords
💡React
💡Fragments
💡JSX
💡Functional Component
💡DOM
💡Enclosing Tag
💡Key Attribute
💡Shorthand Syntax
💡Table Component
💡Columns Component
💡Warnings
Highlights
Introduction to React fragments and their purpose in grouping child elements without adding extra nodes to the DOM.
Creating a new file 'fragment demo.js' to demonstrate React fragments.
Using the React snippet 'rfc' to create a functional component.
Incorporating the fragment demo component into the app component.
Adding a heading and a paragraph to the fragment demo component.
Encountering the error that JSX expressions must have one parent element.
Solving the error by enclosing multiple elements within a single parent element.
Inspecting the DOM to understand the impact of enclosing tags on the DOM tree.
Using React fragments to prevent the addition of extra nodes to the DOM.
Replacing the enclosing div tag with React fragment in the fragment demo component.
Demonstrating the correct rendering in the browser without extra DOM nodes.
Creating a table component and a columns component to showcase React fragments in a table structure.
Addressing console warnings about invalid DOM nesting by using React fragments.
Using React fragments to eliminate console warnings and improve DOM structure.
Explaining that React fragments can accept the key attribute for rendering lists.
Providing an example of using the key attribute with React fragments for list rendering.
Introducing the shorthand syntax for React fragments using empty tags.
Discussing the limitation of the shorthand syntax regarding the key attribute.
Concluding the video with a summary of React fragments' functionality and benefits.
Transcripts
alright guys now that we have the basics
of react behind us it's time to focus on
some of the topics mentioned under the
Advanced section in the official react
documentation let's start with one of
the more easier topics to understand in
this video let's learn about react
fragments fragments basically lets you
group a list of children elements
without adding extra nodes to the Dom
let us understand what that means with
an example vs code and we'll start off
by creating a new file fragment demo dot
jeaious
within the file I'm going to use the
reactor snippet RFC II to create a
functional component
in the JSX I will simply specify the
text fragment demo in the app component
I will include the fragment demo
component
if you save the files and take a look at
the browser you should be able to see
the text fragment demo now let's go back
to the fragment demo component and add a
few more elements in the JSX now I want
to convert the text fragment demo into a
heading so I will replace the div tag
with an h1 tag
right after the heading I want to add a
simple description using a paragraph tag
this describes the fragment demo
component
but when I do this we get a red squiggly
line at the closing parenthesis of the
return statement and when I hover on
that you can see that it says JSX
expressions must have one parent element
if you save the file and take a look at
the browser you can see that the
application is broken as well and the
error message points to the same thing
adjacent JSX elements must be wrapped in
an enclosing tag so anytime your
component has to return multiple
elements you have to enclose them in a
single parent element so let's add that
in closing div tag
when I format it you can see that we
have an enclosing dip tag and the each
one and the paragraph elements are
contained within this enclosing div tag
if you now save the file and take a look
at the browser everything works fine but
if we inspect the element you can notice
that we have the enclosing div tag
included in the Dom tree so between the
div tag from app component and the h1
tag in fragment demo component we have
an additional div tag this is well react
fragments come into picture we can
replace the enclosing div tag with react
fragment and that will prevent the extra
node from being added to the Dom so all
you have to do is in fragment demo
component replace this existing div tag
with react dot fragment
make sure to change the closing tag as
well now if you save the file and go
back to the browser inspect the element
you can see that we no longer have the
div tag between the app component div
tag and the h1 tag and if you go back to
vs code you can see that we are still
returning multiple elements in the JSX
all right now let's take a look at
another example where react fragments
seems much more appropriate I am going
to create two new files so within the
components folder table dot j s and
columns dot j s within the table file
i'm going to use the react snippet r f
c/e to create a functional component for
the GS x i'm going to replace the div
tag with a table tag and within the
table I'm going to add a tee body tag
and then a TR tag to create a row of
data within the row I want to render
columns and the columns will be
maintained in a separate component which
is our columns component so let's go to
column Jes and using the reacts Tibet
our FCE create another functional
component within the JSX I'm going to
add two columns so TD name and another
TD which was because we are returning
multiple elements we need the enclosing
div tag now back in the table component
I will include the columns component
and back in app component I will include
the table component
if you know save all the files and take
a look at the browser you should be able
to see the two columns name and vishwas
if you take a look at the console though
we have warnings and the warning is
validate Dom nesting TD cannot appear as
a child of the dev had basically it is
telling us that it is wrong to have a TD
element as a child of a div tag if I
inspect the element
you can pretty much see that in the dom
tree pd within the div tag and this dip
tag was necessary because we were
returning multiple elements in the JSX
of columns component but hey now we have
the better alternative we can replace
this div tag with react dot fragment so
I'm going to go back to vs code and in
columns component I'm going to replace
the div tag with react dot fragment
if you now go back to the browser you
can see that all console warnings have
disappeared if we inspect the element
you can see that we have the table tag
tbody
TR and then TD there is no div tag in
between the final point on fragments is
that it can accept the key attribute
when rendering lists of items for
example let's assume we have an array of
items stored in a variable called items
then we could have items dot map and
then we have an arrow function the
parameter is item
and the function can return a react
fragment because items in the list need
the key prop though we can specify the
key attribute on react fragment key is
equal to let's say item dot ID
and within the JSX we can have multiple
elements being returned let's say a
heading that says title and then a
paragraph tag that renders
item dot title this is completely
possible as of this recording key
attribute is the only attribute that can
be passed to a reactive fragment the
reactive hopes to add additional
attributes in the future but for now
keep in mind to pass in only the key
attribute
now there is also a shorthand syntax
that you can use for react fragments
instead of react dot fragment you can
use an empty opening tag and an empty
closing tag I will get rid of this items
rendering and now I can replace react
dot fragment with an empty opening tag
and an empty closing tag this basically
represents the idea that it won't add an
actual element to the Dom if you do use
this shorthand syntax though there is
one limitation you cannot pass in the
key attribute so let's save this and
take a look at the browser and you
should still see name and which was the
two columns we have specified so that is
about react fragments fragments let you
group a list of children elements
without adding extra nodes to the Dom
thank you guys for watching don't forget
subscribe I'll see you guys in the next
video
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