All You Need to Know About React Compiler

What if we could build React code without having to worry about concerns with multiple re-rendering and memoization? React 19, the next major release of the popular JavaScript user interface creation library, promises to do just that. By switching to a compiler architecture, it seeks to make the memoization and re-rendering processes simpler. We will examine the benefits of having a compiler in this post, as well as the issues it resolves.

Overview
The React team recently revealed a number of new features that will be included in React 19—such as a React compiler in addition to Actions, Directives, Document Metadata, and Asset Loading—in a blog post.


Additionally, they stated that Instagram is currently running on the new compiler in production. and that the first open source version of the compiler is being worked on by them.

Let's start by comprehending the core ideas behind React.

The Mental Model of React
React works on the fundamental tenet of re-rendering user interfaces in response to modifications in application states. This saves developers from having to write explicit step-by-step instructions on how to change the DOM in order to specify the intended end state of the user interface.


React uses a very clever technique behind the scenes called the virtual DOM. React is therefore able to quickly detect particular DOM elements that need to be updated thanks to this in-memory representation of the user interface. React detects when the state of the application changes, compares the virtual and real DOMs, determines the least amount of changes required, and updates the real DOM precisely.

However, there is a problem with this: React may render again without a reason, which might lead to performance problems.

Superfluous re-renders
Although React's quickness is a benefit, it occasionally results in an excessive number of renders. This is due to the fact that comparing intricate JavaScript data structures like objects and arrays can be computationally costly. React can cause needless re-renders if a component generates a new object or array each time it renders, even if the content hasn't really changed.


Developers must purposefully use memoization techniques to optimize their components in order to prevent this, making sure React updates only when the data actually differs.

Memorization: What is it?
Memorization is a performance improvement strategy in React that includes storing and reusing component output or the outcomes of costly calculations according to their input parameters. Preventing needless component re-rendering is the main objective since it increases overall efficiency.

React provides various ways to memoize a component, and thus preventing it from re-rendering:

React.memo
is a higher order function that lets us skip re-rendering a component when its props are unchanged

const MemoizedComponent = React.memo((props) => {
    // Component logic here
});

useMemo
is a React Hook that lets us cache the result of a calculation between re-renders.

const memoizedResult = useMemo(() => {
    // Expensive computation
}, [dependency1, dependency2]);
useCallback

is a React Hook that lets us cache a function definition between re-renders.

const memoizedCallback = useCallback(() => {
   // Callback logic
}, [dependency1, dependency2]);

Currently, to manually manage which elements of our apps re-render as data changes, developers have to use certain APIs, such as useMemo, useCallback, and memo. It hurts to do this! It necessitates constant maintenance, creates messy code, and is prone to errors. Additionally, this deviates from the central idea of React's mental model. Rather than rendering the user interface declaratively depending on the state of the application, React now requires us to specify how the user interface should be rendered.

The necessity of a compiler
Traditionally, React converts the JSX code into browser-optimized JavaScript files through a procedure known as bundling. This idea is expanded upon in the new compiler. It does a more thorough analysis of your code, taking into account the interdependencies and structure of each component.


As a result, React can automatically optimize re-rendering behaviors without altering the way developers use and perceive React. For this reason, the React team has spent money on an optimizing compiler for React, which makes React more intelligent when it comes to updates.

React presently re-renders when object identity changes, which is one way to look at it. React now re-renders when the semantic value changes thanks to the new compiler, saving on the runtime expense of deep.

The Transition to React Compiler
There is no denying the React compiler's potential advantages. We anticipate a dramatic change in the architecture and optimization of React apps as the project develops, which will result in notable gains in performance, more efficient development processes, and improved code maintainability.


It's a major advancement for the future of React. It is evidence of the React team's constant efforts to enhance the framework and provide developers the tools they need to produce incredible user experiences.