π§ Things I think about when I write React code π§
CC-BY-SA-4.0 License
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
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 contribution to improve react-philosophies
whether big or small is always appreciated.
Note, the following is not an exhaustive list, if you've contributed to this project and you don't see your name included, feel free to submit an PR that adds your name here. Thanks!
π‘ Comments and suggestions
r/reactjs
communityβ Coffee!
π Pull Requests
π Suggested Readings
goldbergyoni/nodebestpractices
, recommended by @rstacruz
react-philosophies
is:
React
code.React
specifically πreact-philosophies
is inspired by various places I've stumbled upon at different points of my coding journey.
Here are a few of them:
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
ESLint
. Enable the rule-of-hooks
and exhaustive-deps
rule to catch React
-specific errors.exhaustive-deps
warnings / errors on your useMemo
's, useCallback
's and useEffect
's. You can try "The latest ref pattern" to keep your callbacks always up-to-date without unnecessary rerenders.map
to display components.tree-shaking
!Typescript
and frameworks such as NextJS
make your life so much easier."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
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?
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 as react-query
or SWR
(or none at all).
Axios
? Axios is a great library with features that are not easily replicable with native fetch
. 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 as redaxios
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 using css variables
instead.
You might not even need Javascript
. CSS is powerful. you-dont-need/You-Dont-Need-JavaScript
"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. The less code the better! (Martin Fowler: YAGNI, C2 Wiki: You Arent Gonna Need It!)
Related section: 2.4 Duplication is far cheaper than the wrong abstraction
1.3.1 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.
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.
1.3.2 Merciless Refactoring. Simple is better than complex.
Is the CL more complex than it should be? Check this at every level of the CLβare individual lines too complex? Are functions too complex? Are classes too complex? βToo complexβ usually means βcanβt be understood quickly by code readers.β It can also mean βdevelopers are likely to introduce bugs when they try to call or modify this code.β- Google Engineering Practices: What to look for in a code review
πββοΈ TIP: Simplify complex conditionals and exit early if you can.
# β Not-so-good
if (loading) {
return <LoadingScreen />
} else if (error) {
return <ErrorScreen />
} else if (data) {
return <DataScreen />
} else {
throw new Error('This should be impossible')
}
# β
BETTER
if (loading) {
return <LoadingScreen />
}
if (error) {
return <ErrorScreen />
}
if (data) {
return <DataScreen />
}
throw new Error('This should be impossible')
πββοΈ TIP: Prefer chained higher-order functions over loops
If there is no discernable performance difference and if possible, replace traditional loops with chained higher-order functions (map
, filter
, find
, findIndex
, some
, etc) Stackoverflow: What is the advantage of using a function over loops?
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.
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.
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.
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.
"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
Context
is not the solution for every state sharing problemuseEffect
s to smaller independent ones (KCD: Myths about useEffect)useCallback
, useMemo
, and useEffect
useCallback
, useMemo
, and useEffect
useState
s, consider using useReducer
if some values of your state rely on other values of your state and previous stateContext
does not have to be global to your whole app. Put Context
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.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
You are tasked to display properties of a right triangle
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.
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 ****/
}
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 ****/
};
Suppose you are assigned to design a component which:
x
or y
(ascending order)maxDistance
(increase by 10
each time, initial value should be 100
)maxDistance
from the origin (0, 0)
useMemo
.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>
</>
)
}
// 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>
</>
)
}
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
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")
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} /></>
}
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.
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)
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.
WavingHand
componentgrey
green
red
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>
}
</>
)
}
// 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
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>
)
}
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.
A particular type of complexity is over-engineering, where developers have made the code more generic than it needs to be, or added functionality that isnβt presently needed by the system. Encourage developers to solve the problem they know needs to be solved now, not the problem that the developer speculates might need to be solved in the future. The future problem should be solved once it arrives and you can see its actual shape and requirements in the physical universe. - Google Engineering Practices: What to look for in a code review
See also: KCD: AHA Programming, C2 Wiki: Contrived Interfaces/The Expensive Setup Smell/Premature Generalization
Premature optimization is the root of all evil - Tony Hoare
One accurate measurement is worth a thousand expert opinions. - Grace Hopper
TL;DR
useMemo
mostly just for expensive calculationsReact.memo
, useMemo
, and useCallback
for reducing re-renders, they shouldn't have many dependencies and the dependencies should be mostly primitive types.React.memo
, useCallback
or useMemo
is doing what you think it's doing (is it really preventing rerendering? Can you demonstrate empirically that using them on your case has significant performance gains? Memoization can sometimes make your app worse, so keep an eye on that!)Context
should be logically separated, do not add too 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.context
by separating the state
and the dispatch
functionlazy loading
and bundle/code splitting
tannerlinsley/react-virtual
or similar)source-map-explorer
or @next/bundle-analyzer
(for NextJS).react-hook-forms
. I think it is a great balance of good performance and good developer experience.useMemo
and useCallback
Write tests. Not too many. Mostly integration. - Guillermo Rauch
TL;DR
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!
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)