React component patterns help us create reusable and extendable components that provide some inversion of control to their parent

Here's a thread of 5️⃣ such patterns

But first let's start with a vanilla <Button> component with "normal" props & how it's used

/thread 🧵👇🏾 ImageImage
1️⃣ Placeholder props

The placeholder props pattern allows the shared component to control its layout & any logic, but give some control to the parent for the display

For our Button comp, the `startIcon` & `endIcon` props can be <svg>, <img> or even other React components

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2️⃣ Polymorphic components

The polymorphic component pattern comes in handy when we need flexibility on the rendered element

For semantic HTML or a11y reasons we may need to change the root element. We can even pass another component for the `as` prop (react-router <Link>)

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3️⃣ Controlled components

The controlled components pattern gives parents flexible control over the shared component's UI logic. The passed in props can make it "controlled" or "uncontrolled"

(see blog post below for more details)

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4️⃣ Render props

The render prop pattern comes in handy when a shared component needs to control layout of any common UI and stateful logic, but the visual look-and-feel is left to the parent component

Render props are typically named `render` or use the `children` prop

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5️⃣ Compound components

When we require full customization of multiple interconnected components, the compound components pattern is very helpful

However it's more complex to implement. IMO it makes the complex use case easier but makes the simple use case more complex

🧵👇🏾 Image
I can only explain so much in 280 characters, so if you wanna learn more I suggest you check out the blog post with all the explanations

What other React component patterns do you use often? 🤔

🧵👇🏾

benmvp.com/blog/picking-r…
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You'll get a weekly frontend-focused email covering JS/TS, React & more!

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More from @benmvp

28 Oct
TypeScript's type system is very powerful because it allows us to express types in terms of other types, including generics

I was looking at the implementation of the TS utilities & learned lots about how to implement generics, so I wanted to share my learnings

/thread 🧵👇🏾
1️⃣ Basic generics

Generic types are like implicit return funcs. They take 1+ params & return a new type

`Partial<>`, `Required<>` & `Readonly<>` take any obj type & return a new obj type w/ property modifiers

We can use them as an example for our own `Mutable<>` util!

🧵👇🏾
2️⃣ Generic constraints

Using `extends` we can restrict what types of params are allowed. It's kinda like providing types of our generic params

`Record<>` limits the `Keys` param to only `string`, `number` or `symbol` cuz JS objects only allow those types as keys

🧵👇🏾
Read 9 tweets
13 Oct
What are some situations for when we can use the `useCallback()` & `useMemo()` Hooks in React components?

Well, one case where we need `useCallback()` is when we call a helper function w/in `useEffect()`, so we need "referential equality" to include it in deps

/thread 🧵👇🏾
I also use `useCallback()` by default when returning a function from a custom Hook cuz I dunno how that function will be used w/in host components

`useCallback()` gives a stable function reference similar to the updater func from `useState()` (the 2nd array element)

🧵👇🏾
The `useMemo()` Hook is similar to `useCallback()` except that it memoizes any value not just functions

So I use `useMemo()` in the same situations: when I have a derived object/array that's used in the deps of `useEffect()`

(I like to think of "memoization" as a cache)

🧵👇🏾
Read 8 tweets
22 Jul
The .reduce() method is maybe the most powerful, yet least understood array method. It basically allows us to transform an array into... nearly anything else

Let's re-implement 1️⃣0️⃣ lodash functions to learn more about how for examples on how .reduce works

/thread 👇🏾🧵
1️⃣ sum()

ℹ️ Computes the sum of the values in an array

The function is called a "reducer" & the 2nd param is our initial value

The 1st arg of the reducer is the "accumulator" (the value we're building up). The 2nd is the current array element in the iteration

/thread 👇🏾🧵
2️⃣ countBy()

ℹ️ Creates an object w/ keys that are the array elements and values that are their counts

Here we're turning an array into an object

(can't forget to return the object we're accumulating!)

/thread 👇🏾🧵
Read 13 tweets
19 May
Nope JSX doesn't have a built-in loop construct. Instead it offloads looping to JavaScript & just accepts an array of JSX elements for rendering lists

💡 So in React, to loop we gotta convert an array of data ➡️ array of JSX elements

Let's look at some ways how...

/thread 🧵👇🏾
Calling `.map` on the array is the most popular way to generate that array of JSX elements

And cuz `.map` returns a new array we can inline it directly in the JSX w/o using a var (also very common)

Putting the `.map` inline makes it *feel* like traditional loop templates

🧵👇🏾
Using a regular `for` loop (or `for-of`, `.forEach`, etc) requires a var that we gotta `.push` into

`for` is likely more familiar to JS newcomers but it means we cannot inline the code

...unless we wanna go rogue and put it in an IIFE 🤯 (anyone used one here before???)

🧵👇🏾
Read 7 tweets
23 Mar
Here is a quick React custom Hook that supports copying text to the system clipboard. It also returns a copied/failed status that can be reflected in the UI

(I remember the days when we could only do this w/ Flash 😭)

more details in the thread 🧵👇🏾
useCopyToClipboard returns a copy function that the UI calls when the user wants to copy the text (likely a button click). It updates the status based on the success/failure of writing to the clipboard

It uses useCallback to ensure a stable function reference

🧵👇🏾
It also uses useEffect to set a timeout that will reset the status after a specified amount of time. This basically makes the status fleeting, which is a typical user experience

🧵👇🏾
Read 6 tweets
26 Jan
Have y'all gotten that React warning about state updates after component unmount?

I get it mainly when running unit tests

Happens when:
- Make async request
- Component unmounts
- Response comes back
- Try to update state w/ new data

I've come up w/ 4️⃣ solutions

/thread 🧵👇🏾
Since vanilla JS Promises aren't cancellable the next best thing is to keep track of the mounted state & don't update state if the comp is unmounted

1️⃣ Variable to track mounted state

Quick & dirty, but only works in single useEffect w/ no deps

🧵👇🏾
2️⃣ Ref to track mounted state

All effects can check the ref regardless of if they have deps. Will have to duplicate in multiple components tho

🧵👇🏾
Read 8 tweets

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