React.js Hydration: What It Is and Why It Matters for Your Web Development Projects

Hydration is an important idea in web development that has the potential to greatly enhance website performance. It refers to the process of taking a server-side rendered HTML page and connecting event listeners and data to it on the client side. This procedure allows for faster rendering speeds and a better user experience.

In this blog post, we'll define hydration in web development and look at how it works in React and other popular web frameworks. We'll also go over some recommended practices for introducing and optimizing hydration.

What exactly is hydration?

Hydration is the process of using client-side JavaScript to add application state and interactivity, event listeners to server-rendered HTML. React ,Next.js, Vue, Angular and many other modern JavaScript frameworks and libraries use hydration in various forms. It is a common concept in modern JavaScript frameworks, and each framework may have its own approach to implementing and optimizing the process for seamless client-side rendering. Thehydration APIthat is provided by React will take that HTML and find the respective element to attach the event listeners, effects etc.

The primary benefit of hydration is that it allows for faster loading speeds for web pages. Server-side rendering can help reduce page load times by pre-rendering the basic HTML, but it lacks client-side behavior and interactivity. This is when hydration enters the picture, adding the required client-side functionality to the pre-rendered content.

React Hydration

React is well-known for its fast hydration process. React employs a virtual DOM (Document Object Model) to update only the areas of the page that requires hydrating, rather than re-rendering the entire page with each update. This means that, while hydration can be a long operation, React's virtual DOM speeds it up and optimizes it.

To acquire the initial HTML for hydration in React, you must first render your component on the server(when digging deep. In a regular application this is done internally). Then, on the client side, use the hydrateRoot() function to attach the event listeners and data to the HTML.

hydrateRoot() lets you display React components inside a browser DOM node whose HTML content was previously generated by react-dom/server. As an example, consider the following:

index.js

This is the standard index.js file where everything gets rendered, and we will render the App component using hydrateRoot(). Syntax is like this:

const root = hydrateRoot(domNode, reactNode, options?)

Now, let's create a modal in the App.js file.

This is a simple modal. I am using the useState hook from React that lets us store any type of data we want. In this case storing false, which is a Boolean data type. This is the initial value we start with, meaning the modal will be hidden unless someone clicks.

Then, we attach an onClick event listener to the button element and pass a callback function. There are other ways of doing this; it's your preference. I am calling a handleModal function when the button is clicked. Inside this function, we use the state setter function. Every time you create a state using useState, you will get access to this setter function. This is used to change the state accordingly.

The setter function also takes a callback in which we can get the previous value of the state. Then, I am just simply negating it. This means if the previous value was false, then it will negate to true, and our modal will show.

I am using conditional rendering here inside curly braces, saying that unless isOpenModal is true, don't render the part inside the braces. The && operator stops executing the next part unless the condition is truthy. This is becoming React class. Let's get back to the topic. So, what do you think the react-dom/server will render this in HTML?

This is it - plain HTML, no listeners, no handlers. Ignore the CDNs. If this is the case, how do we interact then? We have bundle.js where the JavaScript code is. This JavaScript gets executed on the client side after the pre-render and attaches everything client-specific in the HTML. This process is hydration.

Other Web Frameworks' Hydration Process:

Hydration is also supported by prominent web frameworks such as Angular, Vue.js, and Svelte. The implementation of hydration, however, may differ between various frameworks.

For example, Angular's solution to hydration is building a separate bundle of JavaScript code on the server that contains all of the essential data for hydration. This bundle is subsequently delivered to the client along with the HTML, which can be used to associate event listeners and data with the event.

Vue.js, on the other hand, Vue.js uses its built-in hydration API to move from server-side rendered HTML to fully interactive client-side behavior.Sveltealso supports hydration via its hydrate() method, which adds event listeners and data to HTML content.

Best Practices for Hydration Implementation:

Here are some suggested practices to follow to improve hydration performance:

• Inline event handlers should be avoided because they can cause wasteful re-rendering.
• Reduce the quantity of data transferred from the server to the client, as this can affect load times.
• To prevent slowing down the hydration process, choose efficient JavaScript modules and frameworks.
• To ensure that your hydration process is working properly, thoroughly test it.

Finally, hydration is an important part of web construction. It improves user experience by incorporating interactivity and client-side behavior into server-side-produced HTML. You may optimize your hydration process and produce high-performing webpages by following best practices and employing efficient JavaScript libraries and frameworks.