Vue.js Interview Questions and Answers

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100 Vue.js Interview Questions and Answers

  1. What is Vue.js?

    • Answer: Vue.js is a progressive JavaScript framework used for building user interfaces and single-page applications. It's known for its flexibility, ease of learning, and efficient performance. It's designed to be incrementally adoptable, meaning you can integrate it into existing projects easily without a complete rewrite.

  2. What are the core features of Vue.js?

    • Answer: Core features include a declarative rendering system (using templates or JSX), component-based architecture, reactivity system (automatic updates based on data changes), routing, state management (often with Vuex), and a CLI for project scaffolding.

  3. Explain the difference between `v-if` and `v-show` directives.

    • Answer: `v-if` conditionally renders an element based on a condition. It's a full conditional rendering, meaning the element is completely removed from the DOM if the condition is false. `v-show` simply toggles the CSS `display` property of the element. It's faster for frequent toggling but keeps the element in the DOM always.

  4. What is data binding in Vue.js?

    • Answer: Data binding in Vue.js is the mechanism that synchronizes data between the component's data and the DOM. Changes to the data automatically update the view, and changes in the view (through user input, for example) update the data. This is achieved through Vue's reactivity system.

  5. Explain the concept of components in Vue.js.

    • Answer: Components are reusable building blocks in Vue.js. They encapsulate data, logic, and templates, allowing you to break down complex UIs into smaller, manageable pieces. This promotes code reusability, organization, and maintainability.

  6. How do you create a component in Vue.js?

    • Answer: Components can be created using a variety of methods. The most common is defining a JavaScript object with options like `template`, `data`, `methods`, `computed`, etc. They can then be registered globally or locally.

  7. What are computed properties in Vue.js?

    • Answer: Computed properties are reactive dependencies. They are functions that automatically re-compute their value whenever their dependencies change. This is different from methods because they cache their results, only re-computing when necessary, improving performance.

  8. What are watchers in Vue.js?

    • Answer: Watchers are used to monitor changes in a component's data. Unlike computed properties, watchers execute any side effect as a result of data changes - asynchronous operations, logging etc. They are useful for more complex scenarios where you need to perform actions when a specific data property changes, even if it doesn't directly affect the rendered template.

  9. What is Vuex?

    • Answer: Vuex is a state management pattern and library for Vue.js applications. It provides a centralized store for all the components in an application, making state management easier, especially in larger projects.

  10. What is Vue Router?

    • Answer: Vue Router is the official router for Vue.js. It allows you to create single-page applications with multiple views, handling navigation and routing between those views.

  11. Explain the lifecycle hooks in Vue.js.

    • Answer: Lifecycle hooks are methods that are automatically called at different stages of a component's lifecycle. They provide a way to perform actions at specific times, such as initialization, data updates, and cleanup.

  12. What is the difference between `props` and `events` in Vue.js components?

    • Answer: `props` are used to pass data from a parent component to a child component (one-way data flow). `events` are used to pass data from a child component to a parent component (communication upwards).

  13. How do you handle asynchronous operations in Vue.js?

    • Answer: Asynchronous operations (like API calls) are typically handled using promises or async/await within methods or lifecycle hooks. The `loading` state can be managed to update UI during loading and display results after successful completion.

  14. What are slots in Vue.js?

    • Answer: Slots are content distribution mechanisms within components. They allow you to inject content from the parent component into a specific location within the child component's template, enabling customisation and flexibility.

  15. What are mixins in Vue.js?

    • Answer: Mixins are a flexible way to reuse functionalities across multiple components. They contain reusable data, methods, computed properties, lifecycle hooks, etc., that can be merged into other components.

  16. Explain the concept of directives in Vue.js.

    • Answer: Directives are special attributes that begin with `v-` in Vue.js templates. They instruct Vue.js to perform a specific action on the DOM element they are attached to, such as `v-bind`, `v-on`, `v-model`, `v-if`, `v-for`, etc.

  17. What are the different ways to style components in Vue.js?

    • Answer: Components can be styled using scoped styles (CSS within `