Vue 3 Interview Questions and Answers for freshers

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Vue 3 Interview Questions for Freshers

  1. What is Vue.js and what are its key features?

    • Answer: Vue.js is a progressive JavaScript framework for building user interfaces. Its key features include: component-based architecture, reactivity system, virtual DOM, templating, and easy integration with other libraries and tools. It's known for its flexibility, ease of learning, and performance.

  2. Explain the difference between Vue 2 and Vue 3.

    • Answer: Vue 3 offers performance improvements (faster rendering and smaller bundle size) thanks to the Composition API and optimized reactivity system. It also features a better TypeScript support, improved tree-shaking, and a more streamlined API.

  3. What is the Composition API and how does it differ from the Options API?

    • Answer: The Composition API organizes code logically by features, improving code readability and reusability. The Options API groups code by type (data, methods, etc.). Composition API uses `setup()` function, while Options API uses options object.

  4. What is the reactivity system in Vue 3?

    • Answer: Vue 3 uses a proxy-based reactivity system, which tracks changes to data more efficiently than Vue 2's observer-based system. This leads to better performance, especially with large datasets.

  5. Explain the concept of the virtual DOM.

    • Answer: The virtual DOM is a lightweight representation of the actual DOM. Vue uses it to efficiently update the UI by comparing the new virtual DOM with the old one and only updating the necessary parts of the actual DOM, minimizing direct manipulations and improving performance.

  6. What are directives in Vue.js? Give examples.

    • Answer: Directives are special attributes that extend HTML with Vue.js functionalities. Examples include `v-bind` (for dynamic binding), `v-model` (for two-way data binding), `v-on` (for event handling), `v-if` (for conditional rendering), and `v-for` (for list rendering).

  7. How do you handle events in Vue 3?

    • Answer: Events are handled using the `v-on` directive (or the shorthand `@` symbol). The handler function can be defined in the component's methods or using inline functions.

  8. Explain computed properties in Vue 3.

    • Answer: Computed properties are reactive properties that are derived from other reactive data. They are automatically updated when their dependencies change. They are useful for performing calculations or formatting data that needs to be displayed in the template.

  9. What are watchers in Vue 3 and when would you use them?

    • Answer: Watchers are used to react to data changes. Unlike computed properties, they can perform asynchronous operations or have side effects. Use watchers when you need to perform an action in response to a data change that isn't suitable for a computed property (e.g., making an API call).

  10. Explain the lifecycle hooks in Vue 3. Give examples of three.

    • Answer: Lifecycle hooks are functions that are called at specific stages of a component's lifecycle. Examples include `onMounted()` (called after the component is mounted), `onUpdated()` (called after the component is updated), and `onUnmounted()` (called before the component is unmounted).

  11. What is `ref` in Vue 3? How is it different from `reactive`?

    • Answer: `ref` creates a reactive reference to a single piece of data. `reactive` creates a reactive object, making all its properties reactive. `ref` is suitable for single values, while `reactive` is for objects.

  12. How do you create a component in Vue 3?

    • Answer: Components are created as JavaScript objects (using the Options API) or functions (using the Composition API) and then registered with Vue. They typically contain data, methods, computed properties, and lifecycle hooks.

  13. Explain slots in Vue 3.

    • Answer: Slots allow you to insert content into a component from the parent component. They provide a way to customize the rendering of a component without modifying its internal structure.

  14. What are props in Vue 3? How do you pass data to a component using props?

    • Answer: Props are data passed from a parent component to a child component. They are defined in the child component using the `props` option (Options API) or as arguments in the `setup()` function (Composition API). Data is passed from the parent using attribute binding.

  15. What are events in Vue 3? How do you emit events from a child component?

    • Answer: Events are signals that a component emits to communicate with its parent. They are emitted using the `$emit()` method, which takes the event name and any data to pass along.

  16. Explain the concept of a single file component (SFC).

    • Answer: SFCs combine the template, script, and style sections of a Vue component into a single `.vue` file. This makes components more organized and easier to manage.

  17. What are mixins in Vue 3?

    • Answer: Mixins are a way to reuse code across multiple components. They allow you to share methods, computed properties, data, and lifecycle hooks between components.

  18. What is the difference between `v-if` and `v-show`?

    • Answer: `v-if` conditionally renders an element by removing or adding it from the DOM. `v-show` conditionally toggles the `display` style property. `v-if` is more suitable for situations where the element rarely changes, while `v-show` is better for frequently changing visibility.

  19. How do you use `v-for` to iterate over an array in Vue 3?

    • Answer: `v-for="(item, index) in array"` iterates over an array. `item` represents the current array element, and `index` represents its index.

  20. Explain the use of keys in `v-for` loops.

    • Answer: Keys help Vue efficiently update the DOM when using `v-for`. They provide a unique identifier for each item in the array, allowing Vue to track changes and perform minimal DOM updates. It is crucial for performance when dealing with dynamically changing lists.

  21. What are provide/inject in Vue 3?

    • Answer: Provide/inject is a dependency injection mechanism. `provide` makes a value available to all its descendants, while `inject` injects this value into a component. This is useful for sharing data across deeply nested components without prop drilling.

  22. How do you handle asynchronous operations in Vue 3 components?

    • Answer: Asynchronous operations are typically handled using `async/await` within methods or lifecycle hooks. Progress can be displayed by updating component data during the asynchronous process.

  23. How do you perform routing in Vue 3 using Vue Router?

    • Answer: Vue Router is used for routing. You define routes, components associated with those routes, and then use `` to display the active component. Navigation is done via `` components or programmatically using the router instance.

  24. Explain how to use `watchEffect` in Vue 3.

    • Answer: `watchEffect` runs a function whenever its reactive dependencies change. This is useful for performing side effects in response to data changes without explicitly specifying which data to watch.

  25. What is the difference between `watch` and `watchEffect`?

    • Answer: `watch` explicitly specifies which reactive data to observe and runs only when that data changes. `watchEffect` observes all reactive dependencies within its function and runs whenever any of them change.

  26. How do you perform state management in Vue 3? Mention at least two approaches.

    • Answer: Vuex is a dedicated state management library for Vue.js. Alternatively, the Composition API with `reactive` and other reactivity features can be used for simpler state management needs within a component or across a few components using `provide`/`inject`.

  27. What is Teleport in Vue 3?

    • Answer: Teleport allows moving a component's rendered output to a different location in the DOM, outside its normal parent-child hierarchy. This is useful for modals, tooltips, or any component that needs to render in a specific position regardless of its placement in the component tree.

  28. Explain how to use Suspense in Vue 3.

    • Answer: Suspense allows rendering a fallback component while waiting for asynchronous data. It helps improve user experience by showing a loading indicator instead of a blank screen while awaiting data.

  29. What are some common performance optimization techniques in Vue 3?

    • Answer: Use `v-if` over `v-show` where appropriate, optimize `v-for` loops with keys, use `keep-alive` for caching components, and minimize unnecessary DOM updates by using computed properties and watchers efficiently.

  30. How do you integrate Vue 3 with other libraries or frameworks?

    • Answer: Vue 3 is highly flexible and integrates well with other libraries and frameworks, such as Axios for HTTP requests, Pinia for state management, and libraries from other ecosystems via wrappers.

  31. What are some best practices for writing clean and maintainable Vue 3 code?

    • Answer: Use single file components (SFCs), follow a consistent coding style, use proper component structure, utilize the Composition API for better code organization, write unit and integration tests, and leverage Vue's built-in features for state management and routing.

  32. How do you debug Vue 3 applications?

    • Answer: Use your browser's developer tools (especially the Vue Devtools extension), console logging, and debugging tools within your IDE. Vue's error handling and warnings also provide valuable debugging information.

  33. What is the purpose of the `$nextTick` method?

    • Answer: `$nextTick` allows you to execute a function after the next DOM update cycle. This is important for tasks that depend on the DOM being updated before they can proceed, such as accessing DOM elements after a data change.

  34. Explain how to use custom directives in Vue 3.

    • Answer: Custom directives extend the functionality of Vue.js. They are defined as objects with `bind`, `inserted`, `update`, `componentUpdated`, and `unbind` hooks, which run at different stages of a directive's lifecycle.

  35. What is the role of the `setup()` function in Vue 3's Composition API?

    • Answer: The `setup()` function is the entry point for the Composition API. It's where you define reactive data, computed properties, and methods used within the component. It receives props as arguments and returns values that are exposed to the template.

  36. How do you handle form submissions in Vue 3?

    • Answer: Use `v-model` for two-way binding to form inputs. Handle form submission using an event listener on the form element (`v-on:submit` or `@submit`), preventing default behavior (to stop the page from reloading), and then processing the form data.

  37. What are some common testing approaches for Vue 3 components?

    • Answer: Unit tests (testing individual components), integration tests (testing interactions between components), and end-to-end tests (testing the entire application flow) are all common approaches. Testing frameworks like Jest and testing libraries like Vue Test Utils are commonly used.

  38. How do you handle dynamic component rendering in Vue 3?

    • Answer: Use the `component` attribute with dynamic binding (`v-bind:component` or `:component`) to render different components based on a data value.

  39. Explain the use of `toRef` and `toRefs` in Vue 3.

    • Answer: `toRef` creates a reactive reference from a property of a reactive object, while `toRefs` creates an object of reactive references from an object's properties. These functions are useful for working with nested reactive objects in a more manageable way.

  40. What is the difference between `$attrs` and `$listeners` in Vue 3?

    • Answer: `$attrs` contains all the attributes of a parent component that weren't explicitly declared as props in the child component. `$listeners` contains all the event listeners from the parent component. Both are accessible via `setup()` and are useful for passing down attributes or events to nested components.

  41. How do you use TypeScript with Vue 3?

    • Answer: Vue 3 has excellent TypeScript support. You can create `.vue` files with `