Svelte.js Interview Questions and Answers
Freshers / Beginner level questions & answers
Ques 1. What is Svelte.js?
Svelte.js is a modern JavaScript framework that compiles components at build time, resulting in highly optimized and lightweight code for the browser.
Ques 2. What is the purpose of the 'svelte:head' tag?
The 'svelte:head' tag is used to dynamically update the document head with meta tags, title, and other head elements based on the component's state.
Ques 3. How can you perform conditional rendering in Svelte?
Conditional rendering in Svelte can be done using the 'if' and 'else' blocks. For example: {#if condition} ... {:else} ... {/if}
Ques 4. What is the purpose of the 'bind:' directive in Svelte?
The 'bind:' directive in Svelte is used for two-way binding. It establishes a connection between a parent component's property and a child component's property, ensuring changes in one affect the other.
Ques 5. What is the purpose of the 'on:' directive in Svelte?
The 'on:' directive in Svelte is used to handle DOM events. For example: {on: {click: handleClick}}
Ques 6. How does Svelte handle global CSS styles?
Svelte allows you to include global CSS styles using the 'global' keyword. Styles defined with 'global' apply globally across all components.
Ques 7. How can you conditionally apply CSS classes in Svelte?
You can conditionally apply CSS classes in Svelte using the 'class:' directive. For example: {class: active ? 'active' : 'inactive'}
Ques 8. How can you handle form submissions in Svelte?
Form submissions in Svelte can be handled using the 'on:submit' directive. You can prevent the default form behavior and implement your custom logic in the associated function.
Ques 9. What is the purpose of the 'this' keyword in Svelte?
In Svelte, the 'this' keyword refers to the instance of the current component. It can be used to access component methods, properties, and other features.
Ques 10. Explain the purpose of the 'bind:this' directive in Svelte.
The 'bind:this' directive in Svelte is used to bind a DOM element to a variable, making it accessible in your component. Changes to the variable also reflect in the DOM element.
Ques 11. How can you handle HTTP requests in Svelte?
Svelte does not include built-in HTTP request functionality. Developers often use libraries like 'fetch' or 'axios' to handle HTTP requests in Svelte applications.
Intermediate / 1 to 5 years experienced level questions & answers
Ques 12. Explain the concept of reactivity in Svelte.
Reactivity in Svelte refers to the automatic updating of the DOM when the state of a variable changes. Svelte achieves this without the need for a virtual DOM.
Ques 13. Differentiate between Svelte and other front-end frameworks like React or Vue.
Svelte compiles components to highly optimized JavaScript at build time, resulting in smaller bundle sizes and improved performance compared to traditional virtual DOM-based frameworks like React or Vue.
Ques 14. Explain the Svelte component lifecycle.
Svelte components have a simplified lifecycle compared to other frameworks. They do not have lifecycle methods like 'componentDidMount' or 'componentWillUnmount'. Instead, Svelte components have 'onMount' and 'onDestroy' lifecycle functions.
Ques 15. Explain the concept of stores in Svelte.
Stores in Svelte are reactive containers for state management. They allow sharing state between components and automatically update when the state changes.
Ques 16. How does Svelte handle animations?
Svelte has built-in support for animations. You can use the 'animate:' directive to create smooth transitions and animations between state changes in components.
Ques 17. How can you pass data between parent and child components in Svelte?
Data can be passed from parent to child components in Svelte using props. The parent component can bind a variable to a child component property, ensuring updates are reflected in the child.
Ques 18. What are Svelte transitions, and how do you use them?
Svelte transitions enable smooth animations during element insertion, removal, or state changes. You can use 'in:' and 'out:' directives to specify transition effects.
Ques 19. Explain the role of the 'key' attribute in Svelte's each block.
The 'key' attribute in Svelte's each block is used to uniquely identify elements during iteration. It helps Svelte efficiently update the DOM when the list changes.
Ques 20. What is the purpose of the 'context' API in Svelte?
The 'context' API in Svelte allows components to communicate indirectly by sharing state with their descendants. It's useful for avoiding prop drilling.
Ques 21. What is the purpose of the 'use:' directive in Svelte?
The 'use:' directive in Svelte is used to apply actions to DOM elements. Actions are functions that can perform side effects, like animating or interacting with the DOM.
Ques 22. How can you handle route parameters in Svelte?
Svelte allows you to handle route parameters using the '$route' store. You can subscribe to changes in route parameters and update your component's state accordingly.
Ques 23. How does Svelte handle code splitting?
Svelte supports automatic code splitting, meaning that only the components used in a specific route or part of your application are included in the final bundle.
Ques 24. How can you handle side effects in Svelte?
Side effects in Svelte can be handled using lifecycle functions like 'onMount' and 'onDestroy'. These functions are suitable for performing actions when a component is mounted or unmounted.
Ques 25. What are slots in Svelte, and how do you use them?
Slots in Svelte allow you to create reusable components with placeholders for content. They provide a way to pass content into a component from its parent.
Ques 26. What is the purpose of the 'slot' attribute in Svelte?
The 'slot' attribute in Svelte is used to define named slots in a component. It allows the parent component to provide content for specific areas of the child component.
Experienced / Expert level questions & answers
Ques 27. Explain the purpose of the 'await' block in Svelte.
The 'await' block in Svelte is used for asynchronous logic. It allows you to await a Promise and handle the resolved value or catch errors within the template.
Ques 28. Explain the difference between reactive declarations and statements in Svelte.
Reactive declarations in Svelte create reactive variables based on dependencies, while reactive statements directly execute code when dependencies change. Declarations use '$:' syntax, and statements use '{# ... }'.
Ques 29. What is the role of the '$:` syntax in Svelte?
The '$:`` syntax in Svelte is used for two-way binding. It allows you to create a reactive variable that is both readable and writable within a component.
Ques 30. How can you share state between sibling components in Svelte?
State can be shared between sibling components in Svelte by lifting the state to a common parent and passing it down as props to both siblings.
Most helpful rated by users:
- What is Svelte.js?
- Explain the concept of reactivity in Svelte.
- How can you perform conditional rendering in Svelte?
- What is the purpose of the 'on:' directive in Svelte?
- How does Svelte handle global CSS styles?