react-philosophies
If react-philosophies
helped you in some way, consider buying me a few cups of coffee βββ. This motivates me to create more React
"stuff"! π
You have to think about what is the right way, even when you have the right idea of what the building blocks should be, there is huge flexibility in how you decide to put the whole system together. It is a craft... and it has a lot to do with valuing simplicity over complexity. Many people do have a tendency to make things more complicated than they need to be... The more stuff you throw into a system, the more complicated it gets and the more likely it is not going to work properly. - Barbara Liskov
Table of Contents
- Introduction
- The Bare Minimum
- Design for happiness
- Performance tips
- Testing principles
- Insights shared by others
The way this document is organized
It was actually difficult for me to separate my thoughts into the `design`, `performance`, and `testing`. I noticed that lot of designs intended for maintainability also make your application faster and easier to test. Apologies if the discussion appears to be cluttered at times.
Thanks for all the PRs π, coffee β, recommended readings π, and sharing of ideas π‘ (View contributors)
π‘ Comments, suggestions, violent reactions? I'd love to hear them!
If there's something that you think should be part of my reading list or/and if you have great ideas that you think I should include here, don't hesitate to submit a PR or an issue. Particularly, I've included the section Insights shared by others
, should you wish to add your own ideas π. Broken links, grammar, formatting, and typographical error corrections are also welcome. Any contributions to improve react-philosophies
whether big or small are always appreciated.
π‘ Special thanks to those who took the time to share their thoughts!
- The
r/reactjs
community - Josh W Comeau
- @unpunnyfuns
- @cassidoo
β Coffee!
π Pull Requests
π Readings recommended to me
- ryanmcdermott/clean-code-javascript, 3rs-of-software-architecture, ryanmcdermott/code-review-tips
- Ben Moseley and Peter Marks: Out of the Tar Pit (2006), recommended by @icyjoseph
goldbergyoni/nodebestpractices
, recommended by @rstacruz- Dan Abramov: Writing Resilient Components, recommended by Mon Quindoza
- Matthieu Kern: Stop checking if your component is mounted, recommended by @Pierre-CLIND
π§ 0. Introduction
react-philosophies
is:
- things I think about when I write
React
code. - at the back of my mind whenever I review someone else's code or my own
- just guidelines and NOT rigid rules
- a living document and will evolve over time as my experience grows
- mostly techniques which are variations of basic refactoring methods, SOLID principles, and extreme programming ideas... just applied to
React
specifically π
react-philosophies
is inspired by various places I've stumbled upon at different points of my coding journey.
Here are a few of them:
- Sandi Metz
- Kent C Dodds
- Zen of Python (PEP 20), Zen of Go
- trekhleb/state-of-the-art-shitcode, droogans/unmaintainable-code, sapegin/washingcode-book, wiki.c2.com
As a seasoned developer I have certain quirks, opinions, and common patterns that I fall back on. Having to explain to another person why I am approaching a problem in a particular way is really good for helping me break bad habits and challenge my assumptions, or for providing validation for good problem solving skills. - Coraline Ada Ehmke
π§ 1. The Bare Minimum
1.1 Recognize when the computer is smarter than you
- Statically analyze your code with
ESLint
. Enable therule-of-hooks
andexhaustive-deps
rule to catchReact
-specific errors. - Enable "strict" mode. It's 2022.
- Be honest about your dependencies. Fix
exhaustive-deps
warnings / errors on youruseMemo
's,useCallback
's anduseEffect
's. You can try "The latest ref pattern" to keep your callbacks always up-to-date without unnecessary rerenders. - Always add keys whenever you use
map
to display components. - Only call hooks at the top level. Donβt call Hooks inside loops, conditions, or nested functions.
- Understand the warning "Can't perform state update on unmounted component". facebook/react/pull/22114
- Prevent the "white screen of death" by adding several error boundaries at different levels of your application. You can also use them to send alerts to an error monitoring service such as Sentry if you want to. (Accounting for Failures In React)
- There is a reason why errors and warnings are displayed in the console.
- Remember
tree-shaking
! - Prettier (or an alternative) formats your code for you, giving you consistent formatting every time. You no longer need to think about it!
Typescript
will make your life so much easier.- I highly recommend Code Climate (or similar) for open-source repositories or if you can afford it. I find that automatically-detected code smells truly motivates me to reduce the technical debts of the application I'm working on!
NextJS
is an awesome framework.
1.2 Code is just a necessary evil
"The best code is no code at all. Every new line of code you willingly bring into the world is code that has to be debugged, code that has to be read and understood, code that has to be supported." - Jeff Atwood
"One of my most productive days was throwing away 1000 lines of code." - Eric S. Raymond
See also: Write Less Code - Rich Harris, Code is evil - Artem Sapegin
TL;DR
- Think first before adding another dependency
- Eliminate code with techniques not unique to
React
- Don't be clever. YAGNI!
1.2.1 Think first before adding another dependency
Needless to say, the more you add dependencies, the more code you ship to the browser. Ask yourself, are you actually using the features which make a particular library great?
π Do you really need it? View examples of dependencies / code you might not need
-
Do you really need
Redux
? It's possible. But keep in mind that React is already a state management library. -
Do you really need
Apollo client
? Apollo client has many awesome features, like manual normalization. However, it will significantly increase your bundle size. If your application only makes use of features that are not unique to Apollo client , consider using a smaller library such asreact-query
orSWR
(or none at all). -
Axios
? Axios is a great library with features that are not easily replicable with nativefetch
. But if the only reason for using Axios is that it has a better looking API, then consider just using a wrapper on top of fetch (such asredaxios
or your own). Determine whether or not your application is actually using Axios's best features. -
Decimal.js
? Maybe Big.js or other smaller libraries are sufficient. -
Lodash
/underscoreJS
? you-dont-need/You-Dont-Need-Lodash-Underscore -
You might not need
Context
for theming (light
/dark
mode), consider usingcss variables
instead. -
You might not even need
Javascript
. CSS is powerful. you-dont-need/You-Dont-Need-JavaScript
React
1.2.2 Eliminate code with techniques not unique to - Simplify complex conditionals and exit early if you can.
- If there is no discernable performance difference, replace traditional loops with chained higher-order functions (
map
,filter
,find
,findIndex
,some
, etc)
1.2.3 Don't be clever. YAGNI!
"What could happen with my software in the future? Oh yeah, maybe this and that. Letβs implement all these things since we are working on this part anyway. That way itβs future-proof."
You Aren't Gonna Need It! Always implement things when you actually need them, never when you just foresee that you may need them.
See also: Martin Fowler: YAGNI, C2 Wiki: You Arent Gonna Need It!
1.3 Leave it better than you found it
Detect code smells and do something about them if you need to.
If you recognize that something is wrong, fix it right then and there. But if it's not that easy to fix or you don't have time to fix it at that moment, at least add a comment (FIXME
or TODO
) with a concise explanation of the identified problem. Make sure everybody knows it is broken. It shows others that you care and that they should also do the same when they encounter those kinds of things.
π View examples of easy-to-catch code smells
- β Methods or functions defined with a large number of arguments
- β Boolean logic that may be hard to understand
- β Excessive lines of code within a single file
- β Duplicate code which is syntactically identical (but may be formatted differently)
- β Functions or methods that may be hard to understand
- β Classes / Components defined with a large number of functions or methods
- β Excessive lines of code within a single function or method
- β Functions or methods with a large number of return statements
- β Duplicate code which is not identical but shares the same structure (e.g. variable names may differ)
Keep in mind that code smells don't necessarily mean that code should be changed. A code smell just informs you that you might be able to think of a better way to implement the same functionality.
1.4 You can do better
πββοΈ TIP: Remember that you may not need to put your state
as a dependency because you can pass a callback function instead.
You don't need to put setState
(from useState
) and dispatch
(from useReducer
) in your dependency array for hooks like useEffect
and useCallback
. ESLint will NOT complain because React guarantees their stability.
π View example
β Not-so-good
const decrement = useCallback(() => setCount(count - 1), [setCount, count])
const decrement = useCallback(() => setCount(count - 1), [count])
β
BETTER
const decrement = useCallback(() => setCount(count => (count - 1)), [])
πββοΈ TIP: If your useMemo
or useCallback
doesn't have a dependency, you might be using it wrong.
π View example
β Not-so-good
const MyComponent = () => {
const functionToCall = useCallback(x: string => `Hello ${x}!`,[])
const iAmAConstant = useMemo(() => { return {x: 5, y: 2} }, [])
/* I will use functionToCall and iAmAConstant */
}
β
BETTER
const I_AM_A_CONSTANT = { x: 5, y: 2 }
const functionToCall = (x: string) => `Hello ${x}!`
const MyComponent = () => {
/* I will use functionToCall and I_AM_A_CONSTANT */
}
πββοΈ TIP: Wrapping your custom context with a hook creates a better-looking API
Not only does it look better, but you also only have to import one thing instead of two.
π View example
β Not-so-good
// you need to import two things every time
import { useContext } from "react"
import { SomethingContext } from "some-context-package"
function App() {
const something = useContext(SomethingContext) // looks okay, but could look better
// blah
}
β Better
// on one file you declare this hook
function useSomething() {
const context = useContext(SomethingContext)
if (context === undefined) {
throw new Error('useSomething must be used within a SomethingProvider')
}
return context
}
// you only need to import one thing each time
import { useSomething } from "some-context-package"
function App() {
const something = useSomething() // looks better
// blah
}
πββοΈ TIP: Think about how your component will be used before coding it
Writing APIs is hard. README Driven Development
is one useful technique to help design better APIs. I'm not saying we should RDD religiously, just saying that the idea behind it is great. I find that when I first write the API (how the component will be used) before implementing it, this usually creates a better designed component than when I don't.
π§ 2. Design for happiness
"Any fool can write code that a computer can understand. Good programmers write code that humans can understand." - Martin Fowler
"The ratio of time spent reading versus writing is well over 10 to 1. We are constantly reading old code as part of the effort to write new code. So if you want to go fast, if you want to get done quickly, if you want your code to be easy to write, make it easy to read." β Robert C. Martin (Not saying I agree with his political views)
TL;DR
- π Avoid state management complexity by removing redundant states
- π Pass the banana, not the gorilla holding the banana and the entire jungle (prefer passing primitives as props)
- π Keep your components small and simple - the single responsibility principle!
- π Duplication is far cheaper than the wrong abstraction (avoid premature / inappropriate generalization)
- Avoid prop drilling by using composition (Michael Jackson).
Context
is not the solution for every state sharing problem - Split giant
useEffect
s to smaller independent ones (KCD: Myths about useEffect) - Extract logic to hooks and helper functions
- To break a large component, it might be a good idea to have
logical
andpresentational
components (but not necessarily, use your best judgement) - Prefer having mostly primitives as dependencies to
useCallback
,useMemo
, anduseEffect
- Do not put too many dependencies in
useCallback
,useMemo
, anduseEffect
- For simplicity, instead of having many
useState
s, consider usinguseReducer
if some values of your state rely on other values of your state and previous state Context
does not have to be global to your whole app. PutContext
as low as possible in your component tree. Do this the same way you put variables, comments, states (and code in general) as close as possible to where they're relevant / being used.
π 2.1 Avoid state management complexity by removing redundant states
When you have redundant states, some states may fall out of sync; you may forget to update them given a complex sequence of interactions. Aside from avoiding synchronization bugs, you'd notice that it's also easier to reason about and require less code. See also: KCD: Don't Sync State. Derive It!, Tic-Tac-Toe
π Example 1
πποΈ View the business requirement / problem statement
You are tasked to display properties of a right triangle
- the lengths of each of the three sides
- the perimeter
- the area
The triangle is an object with two numbers {a: number, b: number}
that should be fetched from an API.
The two numbers represent the two shorter sides of a right triangle.
β View not-so-good Solution
const TriangleInfo = () => {
const [triangleInfo, setTriangleInfo] = useState<{a: number, b: number} | null>(null)
const [hypotenuse, setHypotenuse] = useState<number | null>(null)
const [perimeter, setPerimeter] = useState<number | null>(null)
const [areas, setArea] = useState<number | null>(null)
useEffect(() => {
fetchTriangle().then(t => setTriangleInfo(t))
}, [])
useEffect(() => {
if(!triangleInfo) {
return
}
const { a, b } = triangleInfo
const h = computeHypotenuse(a, b)
setHypotenuse(h)
const newArea = computeArea(a, b)
setArea(newArea)
const p = computePerimeter(a, b, h)
setPerimeter(p)
}, [triangleInfo])
if (!triangleInfo) {
return null
}
/*** show info here ****/
}
β View "better" solution
const TriangleInfo = () => {
const [triangleInfo, setTriangleInfo] = useState<{
a: number;
b: number;
} | null>(null)
useEffect(() => {
fetchTriangle().then((r) => setTriangleInfo(r))
}, []);
if (!triangleInfo) {
return
}
const { a, b } = triangeInfo
const area = computeArea(a, b)
const hypotenuse = computeHypotenuse(a, b)
const perimeter = computePerimeter(a, b, hypotenuse)
/*** show info here ****/
};
π Example 2
πποΈ View the business requirement / problem statement
Suppose you are assigned to design a component which:
- Fetches a list of unique points from an API
- Includes a button to either sort by
x
ory
(ascending order) - Includes a button to change the
maxDistance
(increase by10
each time, initial value should be100
) - Only displays the points that are NOT farther than the current
maxDistance
from the origin(0, 0)
- Assume that the list only has 100 items (meaning you don't need to worry about optimization). If you're working with really large numbers of items, you can memoize some computations with
useMemo
.
β View a not-so-good Solution
type SortBy = 'x' | 'y'
const toggle = (current: SortBy): SortBy => current === 'x' ? : 'y' : 'x'
const Points = () => {
const [points, setPoints] = useState<{x: number, y: number}[]>([])
const [filteredPoints, setFilteredPoints] = useState<{x: number, y: number}[]>([])
const [sortedPoints, setSortedPoints] = useState<{x: number, y: number}[]>([])
const [maxDistance, setMaxDistance] = useState<number>(100)
const [sortBy, setSortBy] = useState<SortBy>('x')
useEffect(() => {
fetchPoints().then(r => setPoints(r))
}, [])
useEffect(() => {
const sorted = sortPoints(points, sortBy)
setSortedPoints(sorted)
}, [sortBy, points])
useEffect(() => {
const filtered = sortedPoints.filter(p => getDistance(p.x, p.y) < maxDistance)
setFilteredPoints(filtered)
}, [sortedPoints, maxDistance])
const otherSortBy = toggle(sortBy)
const pointToDisplay = filteredPoints.map(
p => <li key={`${p.x}|{p.y}`}>({p.x}, {p.y})</li>
)
return (
<>
<button onClick={() => setSortBy(otherSortBy)}>
Sort by: {otherSortBy}
<button>
<button onClick={() => setMaxDistance(maxDistance + 10)}>
Increase max distance
<button>
Showing only points that are less than {maxDistance} units away from origin (0, 0)
Currently sorted by: '{sortBy}' (ascending)
<ol>{pointToDisplay}</ol>
</>
)
}
β View a "better" Solution
// NOTE: You can also use useReducer instead
type SortBy = 'x' | 'y'
const toggle = (current: SortBy): SortBy => current === 'x' ? : 'y' : 'x'
const Points = () => {
const [points, setPoints] = useState<{x: number, y: number}[]>([])
const [maxDistance, setMaxDistance] = useState<number>(100)
const [sortBy, setSortBy] = useState<SortBy>('x')
useEffect(() => {
fetchPoints().then(r => setPoints(r))
}, [])
const otherSortBy = toggle(sortBy)
const filtedPoints = points.filter(p => getDistance(p.x, p.y) < maxDistance)
const pointToDisplay = sortPoints(filteredPoints, sortBy).map(
p => <li key={`${p.x}|{p.y}`}>({p.x}, {p.y})</li>
)
return (
<>
<button onClick={() => setSortBy(otherSortBy)}>
Sort by: {otherSortBy} <button>
<button onClick={() => setMaxDistance(maxDistance + 10)}>
Increase max distance
<button>
Showing only points that are less than {maxDistance} units away from origin (0, 0)
Currently sorted by: '{sortBy}' (ascending)
<ol>{pointToDisplay}</ol>
</>
)
}
π 2.2 Pass the banana, not the gorilla holding the banana and the entire jungle
You wanted a banana but what you got was a gorilla holding the banana and the entire jungle. - Joe Armstrong
To avoid falling into this trap, it's a good idea to pass mostly primitives (boolean
, string
, number
, etc) types as props. (Passing primitives is also a good idea if you want to use React.memo
for optimization)
A component should just know enough to do its job and nothing more. As much as possible, components should be able to collaborate with others without knowing what they are and what they do.
When we do this, the components will be more loosely coupled, the degree of dependency between two components will be lower. Loose coupling makes it easier to change, replace, or remove components without affecting other components. stackoverflow:2832017
π Example
πποΈ View the business requirement / problem statement
Create a MemberCard
component that displays two components: Summary
and SeeMore
.
The MemberCard
takes in the prop id
. The MemberCard
consumes the hook useMember
which takes in an id
and returns the corresponding Member
information.
type Member = {
id: string
firstName: string
lastName: string
title: string
imgUrl: string
webUrl: string
age: number
bio: string
/****** 100 more fields ******/
}
The SeeMore
component should display the age
and bio
of the member
.
Include a button to toggle between showing and hiding the age
and bio
of the member
.
The Summary
component displays the picture of the member
.
It also displays his title
, firstName
and lastName
(e.g. Mr. Vincenzo Cassano
).
Clicking the member
's name should take you to the member
's personal site.
The Summary
component may also have other functionalities.
(Example, whenever this component is clicked...
the font, size of the image, and background color are randomly changed...
for brevity let's call this "the random styling feature")
β View a not-so-good solution
const Summary = ({ member } : { member: Member }) => {
/*** include "the random styling feature" ***/
return (
<>
<img src={member.imgUrl} />
<a href={member.webUrl} >
{member.title}. {member.firstName} {member.lastName}
</a>
</>
)
}
const SeeMore = ({ member }: { member: Member }) => {
const [seeMore, setSeeMore] = useState<boolean>(false)
return (
<>
<button onClick={() => setSeeMore(!seeMore)}>
See {seeMore ? "less" : "more"}
</button>
{seeMore && <>AGE: {member.age} | BIO: {member.bio}</>}
</>
)
}
const MemberCard = ({ id }: { id: string })) => {
const member = useMember(id)
return <><Summary member={member} /><SeeMore member={member} /></>
}
β View a "better" solution
const Summary = ({ imgUrl, webUrl, header }: { imgUrl: string, webUrl: string, header: string }) => {
/*** include "the random styling feature" ***/
return (
<>
<img src={imgUrl} />
<a href={webUrl}>{header}</a>
</>
)
}
const SeeMore = ({ componentToShow }: { componentToShow: ReactNode }) => {
const [seeMore, setSeeMore] = useState<boolean>(false)
return (
<>
<button onClick={() => setSeeMore(!seeMore)}>
See {seeMore ? "less" : "more"}
</button>
{seeMore && <>{componentToShow}</>}
</>
)
}
const MemberCard = ({ id }: { id: string }) => {
const { title, firstName, lastName, webUrl, imgUrl, age, bio } = useMember(id)
const header = `${title}. ${firstName} ${lastName}`
return (
<>
<Summary {...{ imgUrl, webUrl, header }} />
<SeeMore componentToShow={<>AGE: {age} | BIO: {bio}</>} />
</>
)
}
Notice that in the β
"better" solution"
, SeeMore
and Summary
are components that can be used not just by Member
. It can be used perhaps by other objects such as CurrentUser
, Pet
, Post
... anything that needs those specific functionality.
π 2.3 Keep your components small and simple
What is the single responsibility principle?
A component should have one and only one job. It should do the smallest possible useful thing. It only has responsibilities that fulfill its purpose.
A component with various responsibilities is difficult to reuse. If you want to reuse some but not all of its behavior, it's almost always impossible to just get what you need. It is also likely to be entangled with other code. Components that do one thing which isolate that thing from the rest of your application allows change without consequence and reuse without duplication.
How to know if your component has a single responsibility?
Try to describe that component in one sentence. If it is only responsible for one thing then it should be simple to describe. If it uses the word βandβ or βorβ then it is likely that your component fails this test.
Inspect the component's state, the props and hooks it consumes, as well as variables and methods declared inside the component (there shouldn't be too many). Ask yourself: Do these things actually work together to fulfill the component's purpose? If some of them don't, consider moving those somewhere else or breaking down your big component into smaller ones.
(The paragraphs above are based on my 2015 article: Three things I learned from Sandi Metzβs book as a non-Ruby programmer)
π Example
πποΈ View the business requirement / problem statement
The requirement is to display special kinds of buttons you can click to shop for items of a specific category. For example, the user can select bags, chairs, and food.
- Each button opens a modal you can use to select and "save" items
- If the user has "saved" selected items in a specific category, that category said to be "booked"
- If it is booked, the button will have a checkmark
- You should be able to edit your booking (add or delete items) even if that category is booked
- If the user is hovering the button it should also display
WavingHand
component - A button should also be disabled when no items for that specific category is available
- When a user hovers a disabled button, a tooltip should show "Not Available"
- If the category has no items available, the button's background should be
grey
- If the category is booked, the button's background should be
green
- If the category has available items and is not booked, the button's background should be
red
- For each category, it's corresponding button has a unique label and icon
β View a not-so-good solution
type ShopCategoryTileProps = {
isBooked: boolean
icon: ReactNode
label: string
componentInsideModal?: ReactNode
items?: {name: string, quantity: number}[]
}
const ShopCategoryTile = ({
icon,
label,
items
componentInsideModal,
}: ShopCategoryTileProps ) => {
const [openDialog, setOpenDialog] = useState(false)
const [hover, setHover] = useState(false)
const disabled = !items || items.length === 0
return (
<>
<Tooltip title="Not Available" show={disabled}>
<StyledButton
className={disabled ? "grey" : isBooked ? "green" : "red" }
disabled={disabled}
onClick={() => disabled ? null : setOpenDialog(true) }
onMouseEnter={() => disabled ? null : setHover(true)}
onMouseLeave={() => disabled ? null : setHover(false)}
>
{icon}
<StyledLabel>{label}<StyledLabel/>
{!disabled && isBooked && <FaCheckCircle/>}
{!disabled && hover && <WavingHand />}
</StyledButton>
</Tooltip>
{componentInsideModal &&
<Dialog open={openDialog} onClose={() => setOpenDialog(false)}>
{componentInsideModal}
</Dialog>
}
</>
)
}
β View a "better" solution
// split into two smaller components!
const DisabledShopCategoryTile = ({ icon, label }: { icon: ReactNode, label: string }) => {
return (
<Tooltip title="Not available">
<StyledButton disabled={true} className="grey">
{icon}
<StyledLabel>{label}<StyledLabel/>
</Button>
</Tooltip>
)
}
type ShopCategoryTileProps = {
icon: ReactNode
label: string
isBooked: boolean
componentInsideModal: ReactNode
}
const ShopCategoryTile = ({
icon,
label,
isBooked,
componentInsideModal,
}: ShopCategoryTileProps ) => {
const [openDialog, setOpenDialog] = useState(false)
const [hover, setHover] = useState(false)
return (
<>
<StyledButton
disabled={false}
className={isBooked ? "green" : "red"}
onClick={() => setOpenDialog(true) }
onMouseEnter={() => setHover(true)}
onMouseLeave={() => setHover(false)}
>
{icon}
<StyledLabel>{label}<StyledLabel/>
{isBooked && <FaCheckCircle/>}
{hover && <WavingHand />}
</StyledButton>
{openDialog &&
<Dialog onClose={() => setOpenDialog(false)}>
{componentInsideModal}
</Dialog>
}}
</>
)
}
Note: The example above is a simplified version of a component that I've actually seen in production
β View a not-so-good solution
const ShopCategoryTile = ({
item,
offers,
}: {
item: ItemMap;
offers?: Offer;
}) => {
const dispatch = useDispatch();
const location = useLocation();
const history = useHistory();
const { items } = useContext(OrderingFormContext)
const [openDialog, setOpenDialog] = useState(false)
const [hover, setHover] = useState(false)
const isBooked =
!item.disabled && !!items?.some((a: Item) => a.itemGroup === item.group)
const isDisabled = item.disabled || !offers
const RenderComponent = item.component
useEffect(() => {
if (openDialog && !location.pathname.includes("item")) {
setOpenDialog(false)
}
}, [location.pathname]);
const handleClose = useCallback(() => {
setOpenDialog(false)
history.goBack()
}, [])
return (
<GridStyled
xs={6}
sm={3}
md={2}
item
booked={isBooked}
disabled={isDisabled}
>
<Tooltip
title="Not available"
placement="top"
disableFocusListener={!isDisabled}
disableHoverListener={!isDisabled}
disableTouchListener={!isDisabled}
>
<PaperStyled
disabled={isDisabled}
elevation={isDisabled ? 0 : hover ? 6 : 2}
>
<Wrapper
onClick={() => {
if (isDisabled) {
return;
}
dispatch(push(ORDER__PATH));
setOpenDialog(true);
}}
disabled={isDisabled}
onMouseEnter={() => !isDisabled && setHover(true)}
onMouseLeave={() => !isDisabled && setHover(false)}
>
{item.icon}
<Typography variant="button">{item.label}</Typography>
<CheckIconWrapper>
{isBooked && <FaCheckCircle size="26" />}
</CheckIconWrapper>
</Wrapper>
</PaperStyled>
</Tooltip>
<Dialog fullScreen open={openDialog} onClose={handleClose}>
{RenderComponent && (
<RenderComponent item={item} offer={offers} onClose={handleClose} />
)}
</Dialog>
</GridStyled>
)
}
π 2.4 Duplication is far cheaper than the wrong abstraction
Avoid premature / inappropriate generalization. If your implementation for a simple feature requires a huge overhead, consider other options. I highly recommend reading Sandi Metz: The Wrong Abstraction.
See also: KCD: AHA Programming, C2 Wiki: Contrived Interfaces/The Expensive Setup Smell/Premature Generalization
π§ 3. Performance tips
Premature optimization is the root of all evil - Tony Hoare
One accurate measurement is worth a thousand expert opinions. - Grace Hopper
TL;DR
- If you think itβs slow, prove it with a benchmark. "In the face of ambiguity, refuse the temptation to guess." The profiler of React Developer Tools (Chrome extension) is your friend!
- Use
useMemo
mostly just for expensive calculations - Use
React.memo
,useMemo
, anduseCallback
for reducing re-renders, they shouldn't have many dependencies and the dependencies should be mostly primitive types - Make sure your
React.memo
,useCallback
oruseMemo
is doing what you think it's doing (is it really preventing rerendering?) - Stop punching yourself every time you blink (fix slow renders before fixing rerenders)
- Putting your state as close as possible to where it's being used will not only make your code so much easier to read but It would also make your app faster (state colocation)
Context
should be logically separated, do not add to many values in one context provider. If any of the values of your context changes, all components consuming that context also rerenders even if those components don't use the specific value that was actually changed.- You can optimize
context
by separating thestate
and thedispatch
function - Know the terms
lazy loading
andbundle/code splitting
- Window large lists (with
tannerlinsley/react-virtual
or similar) - A smaller bundle size usually also means a faster app. You can visualize the code bundles you've generated with tools such as
source-map-explorer
or@next/bundle-analyzer
(for NextJS). - If you're going to use a package for your forms, I recommend
react-hook-forms
. I think it is a great balance of good performance and good developer experience.
View selected KCD articles about performance
- KCD: State Colocation will make your React app faster
- KCD: When to
useMemo
anduseCallback
- KCD: Fix the slow render before you fix the re-render
- KCD: Profile a React App for Performance
- KCD: How to optimize your context value
- KCD: How to use React Context effectively
- KCD: One React Mistake that is slowing you down
- KCD: One simple trick to optimize React re-renders
π§ 4. Testing principles
Write tests. Not too many. Mostly integration. - Guillermo Rauch
TL;DR
- Your tests should always resemble the way your software is used
- Make sure that you're not testing implementation details - things which users do not use, see, or even know about
- If your tests don't make you confident that you didn't break anything, then they didn't do their (one and only) job
- You'll know you implemented correct tests when you rarely have to change tests when you refactor code given the same user behavior
- For the front-end, you don't need 100% code coverage, about 70% is probably good enough. Tests should make you more productive not slow you down. Maintaining tests can slow you down. You get dimishing returns on adding more tests after a certain point
- I like using Jest, React testing library, Cypress, and Mock service worker
View selected KCD articles about testing
- KCD: Testing Implementation Details
- KCD: Stop mocking fetch
- KCD: Common mistakes with React Testing Library
- KCD: Making your UI tests resilient to change
- KCD: Write fewer, longer tests
- KCD: Write tests. Not too many. Mostly integration.
- KCD: How to know what to test
- KCD: Common Testing Mistakes
- KCD: Why you've been bad about testing
- KCD: Demystifying Testing
- KCD: UI Testing Myths
- KCD: Effective Snapshot Testing
π§ 5. Insights shared by others
If you'd like to share some of the things you think about when you write React code that I didn't touch upon, you can submit a PR and add them to this section. Thanks for taking the time to share your ideas!
Josh W Comeau
A similar principle I feel much more strongly about is not to pass setters that have too much power. For example, I might pass an
updateEmail
function instead of asetUser
function. I don't want random components to be able to change things they don't have any business changing.
Not only should a component have a single responsibility, it should also have a clear spot on the spectrum of abstraction. On one end, we have generic building blocks like
<Button>
,<Heading>
,<Modal>
. On the other end, we have one-off templates like<Homepage>
and<ContactForm>
. Every component should have a clear spot on this spectrum. A<Button>
component shoudn't have a user prop, since users are a higher-abstract concept andButton
is a low-abstract component.
(Note, the above is taken from his response to my email... I really appreciate that he took the time to share his ideas π)