React Signals: Understanding Usage and Advantages

Paulo Militante
November 30, 2023

ReactJS introduced the Virtual DOM concept to facilitate responsive UI updates based on state changes. However, as applications scale and deep prop passing between components becomes common, this approach encounters challenges leading to unnecessary re-renders.

Signals in React

Signals, a relatively recent addition to frontend development, offers a pragmatic alternative to conventional state handling. Originating from SolidJS, signals have seamlessly integrated into various frameworks, including ReactJS, thanks to the @preact/signals-react package. This article aims to provide a comprehensive comparison of React’s State and Signals, intending to offer a fresh perspective on scenarios where signals present a more efficient solution.

State vs Signal

To illustrate the distinction between state and signals, let’s delve into a simple yet illustrative example – a counter component implemented using both state and signal.

State Implementation

Consider a counter component where every button click triggers a state update, leading to a full re-render in the case of traditional state handling.

import React, { useState } from 'react'

const StateCounterComponent = () => {
  const [count, setCount] = useState(0)

  return (

You clicked {count} times

<button onClick={() => setCount(prev => prev + 1)}>Click me</button>
) } export default StateCounterComponent

Signal Implementation

However, with signals, even though the value changes, the component remains visually unchanged. This magical phenomenon occurs because signals can update the value in the render function at a very granular level, sparing the component from re-rendering every time.

import React from 'react'
import { useSignal } from '@preact/signals-react'

const SignalCounterComponent = () => {
  const count = useSignal(0)

  return (

You clicked {count.value} times

<button onClick={() => count.value++}>Click me</button>
) } export default SignalCounterComponent

While the implementations may seem similar, the critical distinction lies in how signals enable granular updates, successfully avoiding unnecessary re-renders. In the signal implementation, the component updates only where the signal value is used, showcasing a significantly more efficient approach.

Why use Signals?

The efficiency of signals extends beyond merely avoiding unnecessary re-renders; it encompasses improved performance across various use cases. Signals introduce a paradigm shift in state handling, particularly in scenarios where multiple components need to respond dynamically to changes in a shared state.

The precision of signal updates empowers developers to precisely identify which components should react to a change in state. This fine-tuned control minimizes unnecessary recalculations and renders, resulting in a more responsive and performant application.

In larger applications with intricate component hierarchies, signals shine in their ability to optimize performance. Propagation of changes is limited to components directly affected, preventing the unnecessary re-rendering cascade observed in traditional state management.

Signal Integration

This deep dive into React’s State and Signals underscores the efficiency gains achievable through signals, especially in larger and more complex applications. This change not only enhances performance but also contributes to the overall fluidity of the application.

While the current implementation relies on external packages, the continuous evolution of signals in React suggests that a native implementation may be on the horizon. This development could potentially streamline the integration process, making signals more accessible to a broader audience of React developers.

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