What is indexing of list? | Avoid using index as keys
Summary
TLDRThis video delves into the pitfalls of using indexes as keys in list rendering, a common practice in programming. It explains why indexes should not be used due to their tendency to reset upon any list manipulation such as sorting, adding, or removing elements, which can lead to confusion and errors. The video suggests using unique identifiers or a combination of attributes instead to maintain stability. It also outlines scenarios where using an index might be acceptable, such as in static lists. The presenter emphasizes the importance of adhering to best practices and references React documentation, which advises against using indexes as keys.
Takeaways
- 📚 Never use index as a key in lists because it can lead to complications when the list is manipulated.
- 🔑 Keys should be unique and not based on the index value to maintain consistency.
- 🎯 Create a combination of identifiers for keys to ensure uniqueness, such as combining a string with an index.
- 🛑 Avoid using index as a key when the list is subject to dynamic changes like sorting, adding, or removing elements.
- 🔄 Index values are reassigned whenever the list is re-rendered, which can cause issues with list integrity.
- 🍏 Demonstrated an example where adding an element to the beginning of a list caused all indexes to reset.
- 📈 Provided a practical example to illustrate the problems that can arise from using indexes as keys.
- 🚫 React documentation advises against using indexes as keys due to potential issues with list manipulation.
- ✅ Use indexes as keys only in static scenarios where the list is not expected to change.
- 🔑 When a unique attribute like 'id' is available, it should be used instead of the index for keys.
- 💡 Encourages viewers to comment with questions or additional insights to further the discussion on the topic.
Q & A
Why should we avoid using index as a key in list rendering?
-Using index as a key can lead to complications when the list is manipulated (e.g., items added or removed), as the indexes will be reassigned and cause the entire list to re-render, which can lead to performance issues and incorrect behavior.
What is the recommended way to create unique keys for list items?
-It is recommended to use unique values such as IDs or a combination of attributes (like name and color) to create unique keys for list items, ensuring that each item can be uniquely identified even when the list is reordered or items are added or removed.
What happens when a new element is added to the beginning of a list with index keys?
-When a new element is added to the beginning of a list that uses index keys, the entire list gets re-rendered with new index values, causing the original items to shift in their positions and potentially leading to incorrect rendering.
Can index keys be used in any situation?
-Index keys can be used in very basic scenarios where the list is static and there is no possibility of the list being sorted, having items added or removed, or manipulated in any way.
What are some scenarios where using index as a key is not advisable?
-Using index as a key is not advisable when there are unique values available, when the list is expected to be sorted, or when there will be dynamic addition, deletion, or manipulation of the list items.
What does the video suggest as an alternative to using index as a key?
-The video suggests using a combination of attributes or unique identifiers (like IDs) as an alternative to using index as a key to avoid the issues associated with list manipulation.
How does the video demonstrate the problem with using index as a key?
-The video demonstrates the problem by adding a new element to the beginning of a list that uses index as a key, showing how the indexes are reset and the entire list is re-rendered, leading to incorrect item positions.
What is the default behavior when a list with index keys is manipulated?
-The default behavior when a list with index keys is manipulated is that the entire list gets re-rendered with new index values, which can cause performance issues and incorrect item positioning.
Why is it important to have unique keys for list items in React?
-Unique keys are important in React to help the framework identify which items have changed, are added, or are removed. This allows React to efficiently update the DOM and improve performance.
What does the React documentation say about using index as a key?
-The React documentation advises to avoid using index as a key and suggests using unique identifiers instead, as it can lead to unpredictable results and performance issues when the list is manipulated.
Outlines
🚫 Avoiding Index as Keys in Lists
The video begins by addressing the common practice of using indexes as keys in list rendering, a method that is strongly discouraged. The speaker explains that while rendering lists with keys as indexes might seem straightforward, it can lead to complications. To illustrate this, an example is provided where a list of fruits is rendered with index keys. The video demonstrates the pitfalls of this approach by showing what happens when a new fruit is inserted at the top of the list: the indexes are reset, leading to a re-rendering of the entire list and incorrect association of data with the wrong indexes. The speaker emphasizes the importance of using unique identifiers or a combination of attributes as keys to avoid such issues and ensure the stability and predictability of the UI.
📚 Best Practices for Using Indexes in React
Continuing from the previous discussion, the second paragraph delves into the implications of using indexes as keys and the scenarios where it should be avoided. The speaker provides guidance on when it is acceptable to use indexes, such as in static lists where the order is unlikely to change. However, for dynamic lists where items may be added, removed, or sorted, the use of indexes is strongly advised against. The video highlights the importance of using unique values or a combination of attributes to create unique keys for list items. The speaker also references React's official documentation, which recommends avoiding the use of indexes as keys. The video concludes by encouraging viewers to ask questions or add comments for further discussion, emphasizing the value of community engagement in learning.
Mindmap
Keywords
💡rendering
💡keys
💡index
💡unique
💡implications
💡state
💡re-rendering
💡dynamically
💡performance
💡React
Highlights
The video discusses the implications of using index as keys in list rendering.
It is advised not to use index as a key due to potential issues with list re-rendering.
A key should ideally be a unique identifier, not an index value.
Combining the index with other properties like name can create a unique key.
The video provides an example of list rendering using fruit names and colors.
Adding a property 'id' to each item in the array to demonstrate the use of unique identifiers.
Inserting a new element at the beginning of the list to illustrate the complications of using index as keys.
When a new element is added, the indexes are reset, causing a re-rendering issue.
Indexes are not stable and get reassigned whenever the list is manipulated.
Using indexes as keys can lead to incorrect associations between data and DOM elements.
The video recommends avoiding index as keys for dynamic data manipulation.
Indexes can be used in very basic scenarios where the list is static and not subject to change.
React documentation advises against using indexes as keys.
The video outlines scenarios where using index as keys should be avoided.
Creating unique keys by combining multiple attributes is suggested for better list management.
The importance of understanding the implications of using index as keys for performance is emphasized.
The video concludes by inviting viewers to ask questions or add more insights in the comments.
Transcripts
hey guys
another day another video we have seen
what uh rendering of list we have seen
what are keys and now today we are gonna
see
what are indexing of this list and why
we should avoid using index as keys so
without wasting any time let's dive into
this video if you're new to this channel
what you know what to do you have to
subscribe to this channel and give this
video a like
[Music]
so in the previous example we saw that
we rendered some list and keys and keys
as
index right we just rendered a key as an
index but
a surprise comes that we should never
use index as key now why is that we are
going to see in this video
uh let's start with what are the
implications of using index as
key okay so the key should not have this
index value
in real life scenarios what we usually
do we just make a simple
combination of these keys like something
like this so what i'll do i'll just add
a string index okay with a combination
something like my name as well so fruit
oops fruit.name and food.color so this
will give you a good combination and it
will also make your list
keys unique
and hence it will not have any kind of
implication so what are the implications
that we are going
what are the implications that we are
talking about here are that we should
not use index you will see in the
following example so let me just modify
this example a bit we still have the
same apple pear and mango okay as my
[Music]
values into my array and we are just
rendering the same thing we are just
simply rendering it 0 1 2 let me quickly
add something like a property called as
id which is
1
id 2
id 3
okay and i'll simply print this
id as the fruit
dot
id
you can see over here
that
now this is an index value this is my id
and this is the name and this is the
color color right now we don't need it
so let's not make more confusing over
here we'll just simply remove the color
so as to understand
this is my index value the first value
is index the second value is id the
third value is my
name
so i'll simply add a button
on click
i'll say
insert
at top
so i'm not going to do anything i'm just
simply going to add a
hard coded value
just to show you what are the
complications of using index
so before i do that okay this should be
something the fruit should be in my
state because i'm changing the state
right now and i want my uh dom to be
updated
and doing something like this will never
make any changes on my dom and hence
what i'll do this is a constant i'll
just say simply
temporary fruits
[Music]
a simple constant but i'll create a
state
state
and this would be my fruits
fruits
use date
i
we import it from react and the default
value should always be my
this list
if you just see nothing has changed only
the add button is
here we just haven't simple add button
if you want to see what is happening to
the ad if that is working or not we'll
simply say insert
we just added a simple console if you
try yes insert is working
absolutely beautiful
now
by clicking on this add button we are
just going to add let's say another new
element peach or anything at the very
beginning of this before apple and let's
see what is going to happen to our list
what is going to be happening to our
indexes the list and everything
i'll just create a simple
object constant
simple object
equal to
i have a new id that is 4
i have a new name so it will be it would
be a new fruit like guava or anything
and let's say that color would be
green
this is a simple object i just want to
push this object into my fruits
so what i will do i'll just say
set
fruits
[Music]
the existing fruits whatever existing
fruits are there
let it be oops
we are just going to push it in an array
and with that
i'll just simply add my simple object
i hope this works let's see
yes so the new index is here
and the id is here and my
the new element is added at the
end of my
list but we want at the end no we just
simply want it at the very beginning so
i'll just add it at the beginning and
then expand the rest of my object this
is also going to work let me quickly
refresh now when i am going to
look at it very carefully
these are existing
indexes that are already there so 0 is
the zero index is for apple one index is
for pair two indexes for mango now three
even though i'm adding at the very top
it should be three at the
very beginning which should be given to
the
but when i click add
it breaks
there is no error but again the whole
indexes is reset
zero goes to gawa one goes to apple two
goes to pair and three goes to mango
this is the reason we should avoid using
indexes you see what is happening it is
guessing the whole list is getting
re-rendered or in short the whole list
is getting the new index values okay so
gamma is getting like zero apple is
getting one pair is getting two mango is
getting
three even though ids are different
irrespective of of whatever the ids are
but the indexes are again reset from
zero to and so on okay whenever we do
something like this or whenever we sort
the list whenever we add something
whenever we remove something
our indexes get reassigned
that's the reason we should always and
always
avoid
using
index as a key
so when should we use it and when we
should not so i said that you should
avoid using it but you can also use it
in very basic scenarios when you know
that there is nothing uh your table or
your whole data your uh your list is
never going to be sorted something is
never going to be added dynamically in
between the list something is never
going to be popped out from the list in
between so when these scenarios are
there you can use
index because it is very simple okay
it's a simplest thing
but when you know that your data is
going to be populated dynamically
something is going to come in between
the listing is going to be jumbled up
sometime in the future then you should
always avoid index which is a very good
practice overall avoiding index it is
itself a good practice
even if you go to the react official
documentation there it is mentioned that
you should try and avoid using indexes
so let's see when what are these
important things you should not use
index in the following scenarios the
number one is
when you have unique value or at least a
combination to create unique values
try avoiding index so at the very
beginning what we saw we we did a
combination of like name and index you
can do that it is absolutely perfect it
is absolutely fine and it's a very good
way when you don't have a unique
attribute like i have an id as a unique
value but even though when you don't
have a unique value in your list you can
use some other combinations which makes
it more unique
the second scenario would be there
should not be sorting
addition
deletion
or any kind of manipulation of the list
dynamically
in the near future in your example
then you should avoid using
index this was a short video but it was
a very important video from the
perspective of performance
you get something out from it if you
have any questions regarding index why
again or if you just want to add
something more to this video please
mention it in the comment if i missed
something on the other thing i love your
comments and i love replying to them
thank you so much i hope this was
interesting
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