Vue.js Interview Questions

1. What is Vue.js and how does it differ from React and Angular?

2. What is the Vue instance and how does the application lifecycle work?

3. What are Vue components and how do you register them globally vs locally?

4. What is the difference between the Options API and the Composition API in Vue?

5. What is reactivity in Vue and how does the reactivity system work under the hood?

6. What is the difference between ref and reactive in Vue 3?

7. What are computed properties in Vue and how do they differ from methods?

8. What are watchers in Vue and when should you use watch vs watchEffect?

9. What is two-way binding in Vue and how does v-model work?

10. What is the difference between v-if and v-show in Vue?

11. How does list rendering with v-for work and why is the key attribute important?

12. What are props in Vue and how does one-way data flow work?

13. How do child components emit events to parents in Vue?

14. What are slots in Vue and how do named and scoped slots work?

15. What are Vue lifecycle hooks and in what order do they run?

16. What is the difference between provide/inject and props in Vue?

17. What is Vue Router and how does client-side routing work?

18. What are navigation guards in Vue Router?

19. What is Vuex/Pinia and how does centralized state management work in Vue?

20. What is the difference between Vuex and Pinia?

21. What are Vue directives and how do you create a custom directive?

22. What is the virtual DOM in Vue and how does the diffing algorithm work?

23. What are Vue mixins and why does the Composition API often replace them?

24. How does teleport work in Vue 3?

25. What is a Vue single-file component (SFC) and how is it structured?

26. How does scoped CSS work in Vue single-file components?

27. What is the difference between dynamic and async components in Vue?

28. How do you optimize the performance of a Vue application?

29. What is nextTick in Vue and when do you need it?

30. What are the key differences between Vue 2 and Vue 3?

31. When should you use shallowRef, shallowReactive and markRaw in Vue 3?

32. How do you find and fix memory leaks in a Vue application?

33. What causes hydration mismatch errors in server-rendered Vue and how do you fix them?

34. How does Suspense work in Vue 3 and what are its caveats?

35. How do template refs and defineExpose work with <script setup>?

36. How do you test Vue components with Vue Test Utils?

37. What are toRef, toRefs and customRef, and when would you use each?

38. How does KeepAlive work and when does caching a component cause bugs?

39. What do v-memo and v-once do, and when are they worth using?

40. How do you handle errors globally in a Vue application?

41. How do you type props, emits and generic components in Vue with TypeScript?

42. How do you prevent XSS and other client-side vulnerabilities in a Vue app?

43. Why does destructuring a reactive object lose reactivity, and how do you keep it?

44. How does computed caching work in Vue, and when does it mislead you?

45. What do the pre, post and sync watcher flush modes do in Vue?

46. How do you write a Vue composable that cleans up after itself?

47. Why do lifecycle hooks and inject stop working after an await in script setup?

48. How do you type provide and inject safely with InjectionKey?

49. How do you support v-model arguments and custom modifiers on a component?

50. Why does a Vue list re-render more than expected when one row changes?

51. How do custom directive hooks map to the component lifecycle, and where do they leak?

52. Why does a component not reload when only a route param changes?

53. How does route-level code splitting work in Vue, and what does it cost?

54. How do you write a navigation guard that waits for authentication to resolve?

55. Why do you need storeToRefs when destructuring a Pinia store?

56. How do you keep Pinia state from leaking between requests in SSR?

57. How do you share state across components with effectScope instead of a store?

58. How do you use Vue Devtools to find out why an interaction is slow?

59. How do you restore scroll position and list state on back navigation in Vue?

60. When should you use a deep watcher in Vue, and what does it cost?

61. How do you structure Pinia stores to avoid circular dependencies and god stores?