Svelte.js Interview Questions and Answers for freshers

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Svelte.js Interview Questions for Freshers

  1. What is Svelte.js?

    • Answer: Svelte is a radical new approach to building user interfaces. Instead of using a virtual DOM like React or Vue, Svelte compiles your code into small, highly optimized vanilla JavaScript that surgically updates the DOM. This results in smaller bundle sizes, improved performance, and a simpler development experience.

  2. How does Svelte differ from React and Vue?

    • Answer: The key difference lies in how they handle updates. React and Vue manipulate the DOM indirectly through a virtual DOM, while Svelte compiles the code at build time, creating highly optimized code that directly manipulates the DOM. This leads to superior performance in many cases, especially on lower-end devices. Svelte also boasts a simpler syntax and less boilerplate than React or Vue.

  3. Explain the concept of reactivity in Svelte.

    • Answer: Svelte's reactivity is built into its compiler. When a component's data changes, Svelte automatically updates only the necessary parts of the DOM. This is achieved through its compiler's analysis of your code and generation of efficient update logic, eliminating the need for explicit state management mechanisms often seen in other frameworks.

  4. What are Svelte components?

    • Answer: Svelte components are reusable pieces of UI code. They encapsulate HTML, CSS, and JavaScript, promoting modularity and maintainability. They can be nested and composed to create complex UIs.

  5. How do you pass data to a Svelte component?

    • Answer: Data can be passed to Svelte components using props. These are essentially attributes you assign to the component tag. The component then receives these props as variables within its script section.

  6. Explain the role of `$:` in Svelte.

    • Answer: `$:` is used to create reactive declarations. Any expression following `$:` will be evaluated whenever any variable it depends on changes. This enables creating reactive logic without explicitly writing event handlers.

  7. What are actions in Svelte?

    • Answer: Actions are functions that modify DOM elements. They provide a way to attach behavior to elements, such as adding event listeners or manipulating styles. They are typically attached using the `use:action` directive.

  8. How do you handle events in Svelte?

    • Answer: Events in Svelte are handled using standard HTML event attributes, such as `on:click`, `on:mouseover`, etc., directly in the template. The event handler function is passed to the attribute.

  9. What are stores in Svelte?

    • Answer: Stores are a mechanism for managing application state. They allow components to subscribe to changes in data and automatically update when those changes occur. Svelte offers writable, readable, and derived stores to cater to different state management needs.

  10. Explain the difference between `let`, `$:`, and `{#each}` in Svelte.

    • Answer: `let` is used to declare variables within a loop or component scope. `$:` creates reactive statements, re-executing whenever its dependencies change. `{#each}` iterates over an array or iterable object to render multiple elements.

  11. How does Svelte handle transitions and animations?

    • Answer: Svelte offers a built-in transition mechanism using the `transition` directive. This allows you to specify animations for elements entering or leaving the DOM. More complex animations can be achieved using third-party libraries.

  12. What are slots in Svelte components?

    • Answer: Slots allow you to inject content into a component from the outside. This enables creating reusable components that can be customized with different content without modifying their internal structure.

  13. Describe Svelte's built-in styling mechanism.

    • Answer: Svelte allows you to style components using standard CSS within a `