What is indexing of list? | Avoid using index as keys

Summary

This 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

00:00

🚫 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.

05:03

📚 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.

Keywords

💡rendering

Rendering refers to the process of generating an image, video, or any visual representation from a model by means of computer programs. In the context of the video, rendering is used to describe how a list is being displayed or visualized in a user interface, such as a web page. The script mentions rendering a list with keys, which is a common practice in programming to ensure that each element in the list can be uniquely identified and managed.

💡keys

In programming, particularly in the context of the video which seems to be about list rendering in a programming environment like React, keys are unique identifiers used to manage and track the items in a list. Keys help the system to determine which items have changed, are added, or are removed, thus optimizing the re-rendering process. The script discusses the use of indexes as keys, which is not recommended.

💡index

An index is a numerical value that represents the position of an item in an ordered collection, such as an array or list. In the video script, the presenter initially uses index values as keys for rendering a list but then explains the pitfalls of this approach. The index is problematic as a key because it can change when items are added or removed from the list, leading to potential bugs and performance issues.

💡unique

Unique in this context means that each key assigned to an item in the list should be distinct and not duplicated. The video emphasizes the importance of having unique keys to prevent conflicts and ensure the correct identification of list items. The script suggests combining the index with other properties, like 'fruit.name' and 'food.color', to create a unique key.

💡implications

Implications refer to the consequences or effects of a particular action or decision. In the video, the implications of using index as a key are explored, demonstrating that it can lead to issues when the list is modified, such as inserting or removing items, because the indexes will be reassigned, causing the system to misidentify the items.

💡state

In the context of React, state refers to a plain JavaScript object that represents the part of the component that can change over time. The script mentions 'state' when discussing how the list of fruits is managed and updated within the component's state. This is crucial for ensuring that the user interface remains in sync with the underlying data.

💡re-rendering

Re-rendering is the process of re-drawing or re-displaying a user interface component or element when its state or props change. The video script uses the term to illustrate what happens when a list is modified and how using indexes as keys can lead to the entire list being re-rendered with new index values, which can be inefficient and lead to errors.

💡dynamically

Dynamically, in the context of this video, refers to the process of changing data or the structure of the list in real-time, such as adding or removing items. The script warns against using indexes as keys when the list is expected to be manipulated dynamically because it can cause the indexes to be reassigned and lead to incorrect rendering.

💡performance

Performance in this context is related to the efficiency and speed at which a program or system operates. The video discusses the impact of using indexes as keys on performance, suggesting that it can lead to unnecessary re-renders and thus affect the overall performance of the application.

💡React

React is a popular JavaScript library used for building user interfaces, particularly single-page applications. It is mentioned in the script as the likely environment in which the list rendering is being discussed. React has specific best practices for managing lists and keys, which the video aims to address.

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