React Server Components ๐คน
Intro
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๐จโ๐ผ Hello, my name is Peter the Product Manager. I'm here to help you get
oriented and to give you your assignments for the workshop!
Today we're going to implement a React framework based on React Server
Components and Functions! When we're finished with this, you'll have a deep
understanding of the primitives that power React Server Components and Functions
which is the future of React.
We're using unpublished versions of some React packages for this workshop.
We'll be dealing with implementation details that are not part of the public
React API and could change. But the concepts you're learning (which will be
our focus) will stick around forever.
We'll be building this framework without any build tools. This means no
TypeScript, no JSX, no Vite, nothing. We're going to be writing plain JavaScript
and using Node.js/browser native APIs to build our framework.
While this isn't entirely ergonomic, it will help you separate what React is
offering us from the tools we use to build with React.
The goal is for you to understand RSCs free of any abstractions so when you go
to a tool that supports RSCs, you'll have a deep understanding of what's going
on under the hood.
One of the challenges you're going to have to face is understanding the
difference between the requirements of React Server Components and Functions
vs our own choices in this specific implementation of RSCs. RSCs are a very
low-level primitive and there are lots of ways to accomplish the same thing.
Different implementations will have different trade-offs. Try to focus on the
overall concepts and not get too bogged down in the specifics of this
implementation.
Because we're working with such primitive APIs, this will be one of the more
challenging things you've done with React. Keep in mind that frameworks exist
that enable you to offer an awesome user experience with React. This workshop
is about understanding the primitives that power those frameworks now and in the
future.
What are React Server Components?
Let's take a look at a flowchart showing a typical Single Page Application (SPA)
built with React:
Here's a bullet-point text version of this flowchart:
-
User goes to site
- Browser requests document
- Server responds with document
- Browser renders loading spinner
- Server responds with document
- Browser requests client code
- Server responds with client code
- Browser updates UI components
- Server responds with client code
- Browser requests data
- Server generates data response
- Browser sends JSON
- Browser updates UI with JSON data
- Browser sends JSON
- Server generates data response
- Browser requests document
-
User triggers state change (i.e., route change)
- Browser renders pending UI
- Browser requests new data
- Server generates data response
- Browser sends JSON
- Browser updates UI with JSON data
- Browser sends JSON
- Server generates data response
-
User triggers action (i.e., form submission)
- Browser renders pending UI
- Browser makes POST request
- Server performs action with POST body
- Browser sends JSON
- Browser updates UI with JSON data
- Browser sends JSON
- Server performs action with POST body
React server components (RSCs) are a new feature in React that allows you to
stream React components from the server to the client. This means that instead
of requesting data from the server and then rendering it on the client, you can
make a request, have React generate the UI on the server, and send it back to
the client.
Here's a bullet-point text version of the flowchart:
-
User goes to site
- Browser requests document
- Server responds with document
- Browser renders Suspense fallback
- Server responds with document
- Browser requests JSX payload
- Server generates Serialized JSX with
react-server-dom-esm/server.renderToPipeableStream
- Server streams Serialized JSX
- Browser renders streamed UI with
react-server-dom-esm/client.createFromFetch
- Browser requests client component code
- Server responds with client component code
- Browser hydrates client components
- Server responds with client component code
- Browser requests client component code
- Browser renders streamed UI with
- Server streams Serialized JSX
- Server generates Serialized JSX with
- Browser requests document
-
User triggers state change (i.e., route change) NOTE: This only applies once data starts streaming. Until then, state transitions act like a typical SPA.
- Browser renders pending UI with
startTransition
- Browser requests JSX payload
- Server generates Serialized JSX with
react-server-dom-esm/server.renderToPipeableStream
- Server streams Serialized JSX
- Browser updates streamed UI with
react-server-dom-esm/client.createFromFetch
- Browser updates streamed UI with
- Server streams Serialized JSX
- Server generates Serialized JSX with
- Browser renders pending UI with
-
User triggers action (i.e., form submission)
- Browser renders pending UI with
useActionState
- Browser makes POST (via
callServer
)- Server determines action and call with parsed request body
- Server streams Serialized JSX and action return value
- Browser updates streamed UI with
react-server-dom-esm/client.createFromFetch
- Browser updates streamed UI with
- Server streams Serialized JSX and action return value
- Server determines action and call with parsed request body
- Browser renders pending UI with
There are very subtle differences in the flowchart above, but the impact of the
differences is profound.
As a result of this architecture, no code for that UI needs to be sent to the
client and the data doesn't even need to be sent to the client either. This
solves some pretty significant performance and maintainability challenges with
SPAs or even server-rendered apps.
We'll be building this framework as a SPA that uses RSCs on the server. You
can absolutely enhance this further to support server rendering if you like,
but we're going to be skipping that optimization to keep things simple.
Let's go!
๐ต Check out the workshop theme song! ๐ถ
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