100 Vue.js interview questions along with their short answers

Here are 100 Vue.js interview questions along with their short answers:

Vue.js Basics:

1. What is Vue.js?

• Vue.js is an open-source JavaScript framework for building user interfaces and single-page applications.

1. Explain the key features of Vue.js.

• Vue.js features include a component-based architecture, reactivity, virtual DOM, and a simple and intuitive API.

1. What is the Vue.js core library?

• The core library of Vue.js is responsible for the view layer and user interface interactions.

1. What is the purpose of the Vue CLI?

• Vue CLI is a command-line tool for quickly setting up Vue.js projects with best practices and a development environment.

1. What is the Vue.js directive v-bind used for?

• The v-bind directive is used for binding an attribute to an expression, allowing dynamic updates.

1. Explain the Vue.js directive v-model.

• v-model is a two-way binding directive that binds an input element’s value to a data property.

1. What is the purpose of the Vue.js directive v-for?

• The v-for directive is used for rendering a list of items by iterating over an array.

1. What is the Vue.js directive v-on used for?

• The v-on directive is used to listen to DOM events and execute JavaScript expressions.

1. Explain Vue.js single-file components.

• Single-file components encapsulate a component’s template, script, and styles in a single file with the .vue extension.

1. What is the Vue.js virtual DOM?
   • The virtual DOM is an in-memory representation of the actual DOM, used to optimize updates and reduce direct manipulation of the real DOM.

Components:

11. What is a Vue.js component?
    • A component is a reusable, self-contained building block that defines a part of a user interface.
12. How do you create a Vue.js component?
    • You can create a component by using the Vue.component method or by defining it in a single-file component.
13. What is a parent component and a child component in Vue.js?
    • A parent component is a component that contains and manages one or more child components.
14. Explain component communication in Vue.js.
    • Component communication is the process of passing data and events between parent and child components.
15. What is props in Vue.js?
    • Props are custom attributes passed from a parent component to a child component to communicate data.
16. What is the Vue.js this.$emit method used for?
    • this.$emit is used to trigger a custom event from a child component to its parent component.
17. What is the purpose of slots in Vue.js?
    • Slots allow content to be injected into a component from its parent component, making components more flexible.
18. Explain the concept of global components in Vue.js.
    • Global components are components registered globally and can be used in any part of the application without importing them explicitly.
19. What is a dynamic component in Vue.js?
    • A dynamic component is a component that can be switched out or rendered dynamically based on a condition.
20. What is Vue.js mixins?
    • Mixins are a way to share reusable code between components in Vue.js.

Vue Router:

21. What is Vue Router?
    • Vue Router is a library for adding client-side routing to Vue.js applications.
22. How do you configure routes in Vue Router?
    • Routes are configured in a Vue Router by defining an array of route objects.
23. What is the <router-view> component in Vue Router used for?
    • The <router-view> component is a placeholder where route components are rendered.
24. How do you navigate to a different route in Vue Router?
    • You can use the router-link component or the this.$router.push method to navigate to different routes.
25. What is a dynamic route in Vue Router?
    • A dynamic route allows you to match and pass parameters in the route path.
26. What is Vue Router navigation guards?
    • Navigation guards are functions that control the navigation behavior of a route.
27. Explain the difference between global and per-route navigation guards in Vue Router.
    • Global navigation guards apply to all routes, while per-route guards are specific to individual routes.
28. What is lazy loading in Vue Router?
    • Lazy loading allows you to load a route’s component only when the route is accessed.
29. What is Vue Router mode history and hash?
    • The history mode uses regular URLs, while the hash mode uses URLs with a hash fragment.
30. How do you set up a Vue Router in a Vue.js application?
    • You can set up Vue Router by installing it and defining routes in the application.

State Management with Vuex:

31. What is Vuex?
    • Vuex is a state management pattern and library for Vue.js applications.
32. Explain the Vuex store in Vue.js.
    • The Vuex store is a centralized state container that holds the application’s data and provides methods for updating and accessing it.
33. What are actions, mutations, and getters in Vuex?
    • Actions are asynchronous functions that commit mutations, which are synchronous functions that update the state. Getters are used to access state properties.
34. How do you commit a mutation in Vuex?
    • Mutations are committed using commit method in an action, or directly in components using this.$store.commit.
35. What is a strict mode in Vuex?
    • Strict mode in Vuex helps detect and prevent direct mutations of the state.
36. What is a getter in Vuex?
    • Getters are functions that allow you to access computed properties based on the store’s state.
37. How do you dispatch an action in Vuex?
    • Actions are dispatched using the dispatch method in components or other actions.
38. What is the purpose of namespacing in Vuex?
    • Namespacing allows you to create modules with isolated state, actions, mutations, and getters to avoid naming conflicts.
39. How do you install and use Vuex in a Vue.js application?
    • You can install Vuex and define the store in the application, then access it in components using this.$store.
40. Explain the flow of data in a Vuex store.
    • Data flows in a unidirectional manner from the state to the view, with actions committing mutations to update the state.

Computed Properties and Watchers:

41. What are computed properties in Vue.js?
    • Computed properties are functions that calculate a value based on one or more data properties and are cached until their dependencies change.
42. When should you use a computed property instead of a method in Vue.js?
    • Use computed properties when you need to cache and efficiently update a value based on data changes. Use methods for more complex or one-time calculations.
43. What are watchers in Vue.js?
    • Watchers allow you
    to perform asynchronous or expensive operations in response to changes in data properties.
44. What is the difference between computed properties and watchers in Vue.js?
    • Computed properties are used for synchronous calculations and caching, while watchers are used for asynchronous or side-effect-based operations.
45. How do you define a computed property in a Vue component?
    • Computed properties are defined as functions in a component’s computed object.
46. How do you define a watcher in a Vue component?
    • Watchers are defined in the watch option of a component and watch specific data properties.
47. Explain the immediate option in a Vue.js watcher.
    • The immediate option in a watcher forces the callback to be called immediately upon creation.
48. What is deep watching in Vue.js?
    • Deep watching allows a watcher to observe changes in nested properties of an object.
49. How do you use this.$watch in Vue.js?
    • You can use this.$watch to watch data properties or expressions in a component.
50. What is the handler and deep properties in a Vue.js watcher?
    • The handler is the callback function that is executed when the watched data changes. deep is a Boolean property that enables deep watching.

Computed Properties and Watchers:

51. What are mixins in Vue.js?
    • Mixins are a way to share and reuse options between components, such as data, methods, and lifecycle hooks.
52. Explain the order of execution for lifecycle hooks when using mixins in Vue.js.
    • The lifecycle hooks of the component and mixins are called in the order they are merged, starting with the mixin’s hooks and then the component’s hooks.
53. What is scoped CSS in Vue.js single-file components?
    • Scoped CSS ensures that styles defined in a single-file component only apply to the component’s template.
54. What are the benefits of using scoped CSS in Vue.js?
    • Scoped CSS prevents style conflicts and maintains encapsulation, making it easier to reason about styles in a component.
55. What is the Vue.js transition system used for?
    • The Vue.js transition system is used for animating elements entering and leaving the DOM, often used with the <transition> component.
56. What are transition classes in Vue.js?
    • Transition classes are CSS classes applied during transitions, such as v-enter, v-leave, and v-active.
57. How do you apply transitions in Vue.js?
    • Transitions are applied using the <transition> or <transition-group> components with appropriate CSS classes.
58. What is the Vue.js directive v-show used for?
    • The v-show directive toggles the visibility of an element based on a condition.
59. What is the Vue.js directive v-cloak used for?
    • The v-cloak directive is used to prevent uncompiled Vue.js templates from being visible while they load.
60. What are custom directives in Vue.js?
    • Custom directives are custom behavior attached to DOM elements, created using the Vue.directive method.

Vue.js Plugins and Filters:

61. What are Vue.js plugins?
    • Plugins are packages or modules that extend Vue.js with additional features and functionality.
62. How do you install and use a Vue.js plugin?
    • You can install and use a Vue.js plugin by registering it with the Vue.use method in your application.
63. What is the Vue.js filter system used for?
    • Filters allow you to apply text transformations to output in templates, such as formatting dates or currency.
64. How do you create custom filters in Vue.js?
    • Custom filters are created using the Vue.filter method and can be used in templates with the | syntax.
65. What is the filterBy method in Vue.js used for?
    • The filterBy method is used to filter an array of objects based on a specified key and value.
66. What is the Vue.js transition system used for?
    • The Vue.js transition system is used for animating elements entering and leaving the DOM, often used with the <transition> component.
67. What are transition classes in Vue.js?
    • Transition classes are CSS classes applied during transitions, such as v-enter, v-leave, and v-active.
68. How do you apply transitions in Vue.js?
    • Transitions are applied using the <transition> or <transition-group> components with appropriate CSS classes.
69. What is the Vue.js directive v-show used for?
    • The v-show directive toggles the visibility of an element based on a condition.
70. What is the Vue.js directive v-cloak used for?
    • The v-cloak directive is used to prevent uncompiled Vue.js templates from being visible while they load.
71. What are custom directives in Vue.js?
    • Custom directives are custom behavior attached to DOM elements, created using the Vue.directive method.

Vue.js Plugins and Filters:

72. What are Vue.js plugins?
    • Plugins are packages or modules that extend Vue.js with additional features and functionality.
73. How do you install and use a Vue.js plugin?
    • You can install and use a Vue.js plugin by registering it with the Vue.use method in your application.
74. What is the Vue.js filter system used for?
    • Filters allow you to apply text transformations to output in templates, such as formatting dates or currency.
75. How do you create custom filters in Vue.js?
    • Custom filters are created using the Vue.filter method and can be used in templates with the | syntax.
76. What is the filterBy method in Vue.js used for?
    • The filterBy method is used to filter an array of objects based on a specified key and value.
77. How do you create a custom plugin in Vue.js?
    • A custom plugin is created by defining a JavaScript object with an install method and registering it using Vue.use.
78. What is the this.$root property in Vue.js used for?
    • this.$root provides access to the root Vue instance, allowing you to access or modify data and methods defined at the root level.
79. What is the this.$refs property in Vue.js used for?
    • this.$refs is used to access child components or DOM elements within a component.
80. How do you handle errors and exceptions in Vue.js?
    • You can use a global error handler, component-specific error handling, or Vue’s built-in error capture.

Vue.js Advanced Concepts:

81. What is server-side rendering (SSR) in Vue.js?
    • Server-side rendering is a technique used to render Vue components on the server, improving initial page load times and search engine optimization (SEO).
82. What are the benefits of using server-side rendering (SSR) in Vue.js?
    • Benefits
    include faster initial page loads, improved SEO, and better user experiences on slower connections.
83. What is a Vue.js mixin?
    • A mixin is a reusable object that contains component options and can be mixed into multiple components.
84. What is the difference between mixins and custom directives in Vue.js?
    • Mixins provide component options, while custom directives are used to add behavior to DOM elements.
85. What is a render function in Vue.js?
    • A render function is a JavaScript function that generates a Virtual DOM structure, often used for more advanced and dynamic component rendering.
86. Explain the difference between a functional component and a regular component in Vue.js.
    • Functional components are stateless and rely only on their props, whereas regular components have internal state and lifecycle hooks.
87. What is the scopedSlots property in Vue.js used for?
    • The scopedSlots property allows a parent component to pass data and methods to a slot in a child component.
88. What is the Vue.js error boundary feature used for?
    • Error boundaries catch and handle errors that occur during the rendering of a component tree.
89. What is the transition component in Vue.js used for?
    • The transition component provides declarative transition effects for elements entering and leaving the DOM.
90. What are the different types of transitions in Vue.js?
    • Enter/leave transitions, list transitions, and mode transitions are the types of transitions in Vue.js.

Performance Optimization:

91. What are the techniques for optimizing the performance of a Vue.js application?
    • Techniques include using production builds, code splitting, async components, lazy loading, and minimizing reactivity.
92. What is the purpose of using production and development builds in Vue.js?
    • Production builds are optimized for performance and should be used in production environments, while development builds provide additional debugging information.
93. How can you optimize the rendering performance of a Vue.js component?
    • Optimize rendering performance by using v-once, v-if, and v-for with caution, and implementing virtual scrolling.
94. What is code splitting in Vue.js and why is it important for performance?
    • Code splitting is the practice of breaking an application’s code into smaller bundles to reduce initial page load times.
95. What is the purpose of async components in Vue.js?
    • Async components are loaded dynamically, improving initial load times by splitting the code into smaller chunks.
96. How do you implement lazy loading in Vue.js?
    • Lazy loading is implemented by using the import function and dynamically loading components only when needed.
97. What is reactivity in Vue.js, and how can you minimize it for better performance?
    • Reactivity refers to the ability of data to trigger updates in the UI. Minimize reactivity by using Object.freeze, and avoiding deep object watches.
98. What is memoization in Vue.js, and how can it improve performance?
    • Memoization is a technique that caches computed values, reducing redundant calculations and improving performance.
99. How can you use the keep-alive component in Vue.js to cache components for performance?
    • The keep-alive component caches components that are not actively in use, improving navigation performance.
100. What are server-side rendering (SSR) and pre-rendering in Vue.js, and how do they benefit performance?
     • Server-side rendering (SSR) and pre-rendering generate HTML on the server, leading to faster initial page loads and better SEO.