Is Virtual DOM Really Necessary?

What Is the DOM?

Before we dive into whether Virtual DOM is necessary, let’s understand what the DOM actually is and why it matters.

The Document Object Model (DOM) is essentially your browser’s representation of a web page. When your browser loads an HTML file, it doesn’t just display the text - it creates an in-memory object structure that represents every element, attribute, and piece of text on the page.

Think of it like this: if HTML is the blueprint, the DOM is the actual building constructed from that blueprint. And just like you can renovate rooms in a building, you can modify elements in the DOM.

<div id="container">
  <h1>Hello World</h1>
  <input type="text" />
</div>

The browser turns this into a tree of objects:

Document
  └── div (id="container")
      ├── h1
      │   └── "Hello World"
      └── input (type="text")

How Browser Rendering Actually Works

When the DOM changes, the browser goes through several steps to update what you see:

1. Parse HTML → Create DOM
2. Parse CSS → Create CSSOM
3. Combine them → Render Tree
4. Layout → Calculate positions and sizes
5. Paint → Draw pixels
6. Composite → Combine layers and display

The Performance Terms You Should Know

Repaint: When only visual styles change (color, background). The browser just redraws the affected elements.

Reflow: When layout changes occur (width, height, position). The browser has to recalculate positions and potentially affect other elements.

Here’s the important part: modern browsers are already pretty smart about this. When you change one input field, the browser doesn’t repaint the entire page - it only updates what actually changed.

The Vanilla JavaScript Reality

Let’s look at what happens with plain JavaScript:

// Changing an input value
document.getElementById("username").value = "John";

// Changing text content
document.getElementById("counter").innerText = count;

// Changing styles
document.getElementById("button").style.color = "red";

Each of these operations:

• Only affects the specific element
• Causes minimal repaint/reflow
• Doesn’t touch other parts of the page

The browser is already optimized for these kinds of changes. So why did Virtual DOM become a thing?

The Real Problem Virtual DOM Solves

The issue isn’t browser performance - it’s developer productivity and state management complexity.

Vanilla JS Gets Messy Fast

Imagine you’re building a todo app. With vanilla JavaScript, you need to:

function updateTodoList(todos) {
  const container = document.getElementById("todo-list");
  container.innerHTML = ""; // Clear everything

  todos.forEach((todo) => {
    const item = document.createElement("li");
    item.className = todo.completed ? "completed" : "pending";
    item.innerHTML = `
      <span>${todo.text}</span>
      <button onclick="deleteTodo(${todo.id})">Delete</button>
    `;
    container.appendChild(item);
  });
}

Problems with this approach:

• You’re manually tracking what changed
• Easy to forget to update related UI elements
• State and UI can get out of sync
• As the app grows, managing all these updates becomes a nightmare

The React Alternative

With React, you just describe what the UI should look like:

function TodoList({ todos }) {
  return (
    <ul>
      {todos.map((todo) => (
        <li key={todo.id} className={todo.completed ? "completed" : "pending"}>
          <span>{todo.text}</span>
          <button onClick={() => deleteTodo(todo.id)}>Delete</button>
        </li>
      ))}
    </ul>
  );
}

When todos changes, React:

1. Runs the component function again
2. Creates a new Virtual DOM representation
3. Compares it with the previous version (diffing)
4. Updates only the parts that actually changed

Virtual DOM: The Developer Experience Layer

Here’s the key insight: Virtual DOM isn’t primarily about browser performance - it’s about developer productivity.

Virtual DOM enables:

Declarative Programming: You describe what the UI should look like, not how to change it

Automatic State Synchronization: When state changes, UI automatically updates

Predictable Updates: UI = f(state) - given the same state, you always get the same UI

Batched Updates: React can group multiple state changes into a single DOM update

The Modern Debate: Do We Still Need It?

This is where things get interesting. Newer frameworks are questioning whether Virtual DOM is the best approach.

Svelte’s Compiler Approach

Svelte takes a different path. Instead of using Virtual DOM at runtime, it uses a compiler to generate optimized update code:

<script>
  let count = 0;

  function increment() {
    count += 1;
  }
</script>

<button on:click={increment}>
  Count: {count}
</button>

Svelte compiles this to code that directly updates the specific DOM nodes when count changes. No Virtual DOM needed.

SolidJS: Reactive Primitives

SolidJS uses a reactive system where only the specific DOM nodes that depend on changed data get updated:

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

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

The component function runs once, but the {count()} part updates reactively when the signal changes.

Common Misconceptions

Let me clear up some widespread myths:

Myth 1: “Virtual DOM prevents full page reloads”

Reality: Browsers already only update what changes. Virtual DOM’s benefit is automating the “what changed” detection.

Myth 2: “Virtual DOM makes apps faster”

Reality: Virtual DOM adds overhead. The benefit is development speed and maintainability, not raw performance.

Myth 3: “Without Virtual DOM, variables reset on every update”

Reality: This confuses browser rendering with React re-rendering. In vanilla JS, global variables persist through DOM changes.

The Performance Reality Check

Here’s what actually happens with performance:

Vanilla JS: Potentially fastest, but requires manual optimization and careful state management

React with Virtual DOM: Slight overhead from diffing, but automatic optimization and batching

Svelte: Potentially faster than React, with similar developer experience benefits

But here’s the thing: for most applications, this performance difference is negligible. The bottleneck is rarely DOM updates - it’s usually network requests, complex calculations, or poorly optimized algorithms.

Why React Still Uses Virtual DOM

Given that newer approaches exist, why does React stick with Virtual DOM?

1. Ecosystem Lock-in: Millions of developers and thousands of libraries built around React’s model

2. Cross-platform Benefits: Virtual DOM abstraction enables React Native, React Server Components, etc.

3. Incremental Adoption: Changing React’s core architecture would break existing apps

4. Proven Stability: Virtual DOM is a well-understood, debugged approach

Even React team members acknowledge this. Dan Abramov (former React core team) said: “Virtual DOM is a means to an end, not the end itself. The end is good developer experience.”

So… Is Virtual DOM Necessary?

The answer depends on what you’re optimizing for:

Choose Virtual DOM (React) when:

• Working with large teams that know React
• Building complex applications with lots of state
• Need mature ecosystem and tooling
• Cross-platform development is important

Choose compiler-based approaches (Svelte) when:

• Performance is critical
• Bundle size matters
• Team is comfortable with newer technologies
• You want the simplest possible mental model

The Bottom Line

Virtual DOM solved a real problem: making complex UI state management predictable and maintainable. The fact that newer frameworks can achieve similar benefits without Virtual DOM doesn’t invalidate this - it shows the problem is being solved in multiple ways.

The question isn’t whether Virtual DOM is “necessary” in an absolute sense. It’s whether the benefits (declarative programming, automatic state sync, predictable updates) are worth the costs (slight performance overhead, added complexity) for your specific project.

For most developers building most applications, the answer is still yes. Virtual DOM remains one of the most practical ways to build complex UIs without losing your sanity.

But it’s no longer the only way. And that’s a good thing for the web development ecosystem.