Optimizing your components with useSignal

State management is a fundamental part of building React and Preact applications. The useState hook is the most common way to manage state in React components, but there's a new kid on the block that's worth considering: useSignal.

useSignal is part of the @preact/signals library, which provides a way to manage state using reactive principles. In this article, we'll take a closer look at useSignal, compare it with useState, and provide some code examples.

Introduction to useSignal

At its core, a signal is an object with a .value property that holds some value. Accessing a signal's value property from within a component automatically updates that component when the value of that signal changes.

useSignal is a hook that creates a signal and returns the current value of the signal, as well as a function to update the signal's value. Here's an example of how you can use useSignal to manage state in a simple counter component:

import { useSignal } from "@preact/signals";

function Counter() {
  const [count, setCount] = useSignal(0);

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Increment</button>
    </div>
  );
}

In the above example, we are using useSignal to create a stateful value called count, and a setter function called setCount. The initial value of count is 0.

When the Increment button is clicked, the setCount function is called with the updated value of count + 1, which updates the state of count. This in turn triggers a re-render of the component, since the component is subscribed to changes in the count signal.

This is similar to how you would manage state using useState, but with some key differences:

• With useSignal, you don't need to create a separate setter function for updating the state. The useSignal hook returns both the current value of the signal and a function for updating the signal.
• useSignal is optimized for use with Preact's Virtual DOM. When you update a signal, Preact will automatically optimize the updates behind the scenes for you, so you don't need to worry about performance.
• useSignal is designed to work with complex state graphs, so you can use it to manage state at any level of your component tree.

Comparing useSignal and useState

Let's compare useSignal with useState to see the similarities and differences between the two.

Similarities

• Both useSignal and useState are hooks for managing state in React and Preact components.
• Both useSignal and useState return a current value and a function for updating the value.
• Both useSignal and useState trigger a re-render of the component when the state changes.

Differences

• With useSignal, the state is stored in a signal object, which is optimized for use with Preact's Virtual DOM. With useState, the state is stored in a plain JavaScript variable.
• With useSignal, you don't need to create a separate setter function for updating the state. With useState, you need to call the setState function to update the state.
• useSignal is designed to work with complex state graphs, so you can use it to manage state at any level of your component tree.

One key difference between useSignal and useState is how you update the state. With useState, you call the setter function and pass in the new state value. With useSignal, you call the signal itself like a function, passing in the new value as an argument.

Overall, useSignal provides a simpler and more intuitive way to manage state, with better performance and developer ergonomics than useState. However, it may take some time to get used to the slightly different syntax and usage.