Svelte.js Interview Questions and Answers for 5 years experience

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Svelte.js Interview Questions (5 years experience)

  1. What is Svelte? How does it differ from other frameworks like React or Vue?

    • Answer: Svelte is a radical new approach to building user interfaces. Unlike React or Vue, which do the bulk of their work in the browser, Svelte shifts that work into a compile step that happens when you build your app. This results in smaller bundle sizes, improved performance, and less reliance on a virtual DOM. React and Vue manipulate the DOM, leading to overhead. Svelte compiles the code into highly optimized vanilla JavaScript, directly manipulating the DOM only when necessary.

  2. Explain the concept of reactive declarations in Svelte.

    • Answer: Reactive declarations in Svelte are the heart of its reactivity system. By declaring variables using `let`, `const`, or `$:`, Svelte automatically tracks dependencies and updates the DOM whenever those variables change. This eliminates the need for explicit state management mechanisms found in other frameworks. The `$:` syntax creates reactive statements, enabling complex reactive logic based on variable changes.

  3. How does Svelte handle state management? Discuss different approaches.

    • Answer: Svelte's built-in reactivity handles much of the state management implicitly. For simpler applications, directly using reactive declarations is sufficient. For larger applications, you might use a store (like `writable`, `readable`, or `derived` stores from `svelte/store`), which provides a centralized way to manage and share state across components. External libraries like Zustand or Pinia can also be integrated if needed.

  4. Explain Svelte's component lifecycle.

    • Answer: Svelte components have a lifecycle with phases like `onMount`, `beforeUpdate`, `afterUpdate`, `onDestroy`. `onMount` runs after the component is first inserted into the DOM. `beforeUpdate` runs before the component is updated, `afterUpdate` runs after the component updates, and `onDestroy` runs when the component is removed from the DOM. These lifecycle methods allow for performing actions at specific stages of a component's existence, crucial for managing side effects or cleanup.

  5. How do you handle events in Svelte?

    • Answer: Event handling in Svelte is straightforward using standard HTML event attributes directly on elements within the component template. For example, ``. The `handleClick` function would be defined within the component's script section.

  6. Describe Svelte's template syntax.

    • Answer: Svelte's template syntax is HTML-like, allowing you to use standard HTML elements and attributes. It uses curly braces `{}` to embed JavaScript expressions directly into the template. Svelte directives like `{#if}`, `{#each}`, and `{#await}` provide control flow and iteration within the template.

  7. Explain the use of slots in Svelte components.

    • Answer: Slots allow you to inject content into a component from its parent. This enables creating reusable components that can be customized with different content depending on the context. `` tags within a component's template define where the content from the parent will be rendered.

  8. How do you manage component styling in Svelte?

    • Answer: Svelte offers several ways to style components: scoped CSS (using the `