Svelte vs React vs Vue comparison - Practice Questions

Challenge - 5 Problems

❓ component_behavior

intermediate

How does Svelte update the DOM compared to React and Vue?

Consider how Svelte, React, and Vue update the webpage when data changes. Which statement best describes Svelte's approach?

A Svelte compiles components to efficient JavaScript that updates the DOM directly without a virtual DOM.

B Svelte uses a virtual DOM to batch updates and then applies them to the real DOM like React.

C Svelte relies on a reactive system that tracks dependencies but still uses a virtual DOM like Vue.

D Svelte updates the entire DOM tree on every change without optimization.

💡 Hint

Think about whether Svelte uses a virtual DOM or compiles away the framework.

Svelte compiles your code into small, efficient JavaScript that updates the DOM directly. Unlike React and Vue, it does not use a virtual DOM, which makes updates faster and smaller.

❓ state_output

intermediate

What is the output of this Svelte reactive statement compared to React's useState?

Given this Svelte code snippet, what will be the value of count after clicking the button twice?

  <script>
    let count = 0;
    function increment() {
      count += 1;
    }
  </script>
  <button on:click={increment}>Clicked {count} times</button>

A count will be 1 because Svelte batches updates and skips the second increment.

B count will be 2, but the button text updates only after a delay.

C count will remain 0 because Svelte requires special hooks to update state.

D count will be 2, and the button text updates immediately after each click.

💡 Hint

Remember how Svelte tracks reactive variables and updates the UI immediately.

Svelte tracks changes to variables like count automatically. When you click the button, count increases and the UI updates right away without needing extra hooks.

📝 Syntax

advanced

Which Svelte syntax correctly binds a component prop and listens to an event?

Choose the correct Svelte syntax to pass a title prop to a child component and listen for a save event.

A <Child [title]=pageTitle (save)=handleSave />

B <Child :title="pageTitle" @save="handleSave" />

C <Child title={pageTitle} on:save={handleSave} />

D <Child bind:title={pageTitle} listen:save={handleSave} />

💡 Hint

Recall how Svelte uses curly braces for props and on:event for events.

Svelte uses curly braces to pass props and the on:event directive to listen to events. Option C follows this pattern correctly.

🔧 Debug

advanced

Why does this Svelte component fail to update the UI when the array changes?

Look at this Svelte code snippet:

<script>
  let items = [1, 2, 3];
  function addItem() {
    items.push(items.length + 1);
  }
</script>
<button on:click={addItem}>Add Item</button>
<ul>
  {#each items as item}
    <li>{item}</li>
  {/each}
</ul>

Clicking the button does not update the list. Why?

A Because the <code>each</code> block requires a key to update properly.

B Because Svelte does not detect changes when mutating arrays directly; you must assign a new array to trigger updates.

C Because the <code>push</code> method is asynchronous and delays updates.

D Because the <code>addItem</code> function is missing an <code>await</code> keyword.

💡 Hint

Think about how Svelte tracks changes to variables and arrays.

Svelte tracks assignments to variables. Mutating an array with push does not trigger reactivity. You must assign a new array, for example: items = [...items, newItem].

🧠 Conceptual

expert

Which framework's design leads to smaller bundle sizes and faster startup times?

Between Svelte, React, and Vue, which framework's design inherently produces smaller JavaScript bundles and faster page load times, and why?

A Svelte, because it compiles components at build time into minimal JavaScript without a runtime virtual DOM.

B React, because its virtual DOM diffing reduces the amount of JavaScript needed at runtime.

C Vue, because it uses a template compiler that eliminates the need for JavaScript in the browser.

D All three produce similar bundle sizes because they all use virtual DOMs.

💡 Hint

Consider which framework does most work before the browser runs the code.

Svelte compiles your code ahead of time into efficient JavaScript that updates the DOM directly. This removes the need for a large runtime library and virtual DOM, resulting in smaller bundles and faster startup.