Vue interview questions

Reactivity

• How does Vue 3 track changes? Proxies, which is why it catches property addition where Vue 2's `defineProperty` approach could not.
• `ref` versus `reactive` - and why `ref` needs `.value` in script but not in template.
• What happens when you destructure a `reactive` object? You lose reactivity - and `toRefs` is the fix. A very common question.
• Why does replacing an array work while mutating an index sometimes surprises people?
• `shallowRef` and when you would want to opt out of deep reactivity.

computed versus watch

• `computed` for derived values - cached, synchronous, no side effects.
• `watch` for reacting to a change with a side effect - a request, navigation, local storage.
• `watchEffect` and how its automatic dependency tracking differs from an explicit watcher.
• The anti-pattern: using a watcher to set a value that should simply be computed.

Components and composition

• Props down, events up - and why mutating a prop is wrong.
• `v-model` on a component, and what it desugars to.
• Slots, including named and scoped slots.
• `provide`/`inject`, and when it is preferable to prop drilling.
• Composition API versus Options API - and the practical answer that composables give better logic reuse and TypeScript inference, while Options is fine for simple components.
• Writing a composable, and what makes one reusable rather than merely extracted.

Lists, lifecycle and tooling

Why `key` matters in `v-for` and what breaks with an index key, why `v-if` and `v-for` on the same element is discouraged, and the lifecycle hooks you actually use. Then Pinia for state, and the routing questions - navigation guards and lazy-loaded routes. The framework-agnostic ground is in frontend interview questions.

How deep it goes by level

• Junior: the fundamentals above, explained clearly. Nobody expects production scars yet, and saying what you have not done reads better than bluffing.
• Mid-level: the same ground plus an app you have built and a reactivity bug you debugged. Expect follow-ups asking why you made a choice rather than whether you know the syntax.
• Senior: a Vue 2 to Vue 3 migration, and architecture choices across a large codebase. The recall questions get shorter and the judgement questions get longer.

Whatever the level, say your answers out loud rather than reading them. Most of what candidates lose in a Vue interview is lost between knowing something and explaining it under observation - the method is in how to use AI for interview prep.

Where CoPilot Interview fits

Disclosure: we build an interview assistant, so treat this as a disclosed pitch. CoPilot Interview is a native Windows and macOS app that puts suggested answers on your own screen in about two seconds, across coding, system design and behavioral rounds, with a permanent free tier that needs no credit card.

Frequently asked questions

What are the most common Vue interview questions?

How Vue 3 reactivity works with proxies, `ref` versus `reactive`, why destructuring a reactive object loses reactivity, `computed` versus `watch`, component communication with props and events, and the Composition versus Options API trade-off.

Why does destructuring a reactive object break reactivity in Vue?

The reactivity lives in the proxy wrapping the object, not in the values themselves, so extracting a property yields a plain value with no tracking. `toRefs` converts each property into a ref that keeps the connection, which is the standard fix.

What is the difference between computed and watch in Vue?

`computed` derives a cached value from other state and should be free of side effects. `watch` responds to a change by doing something - a request, navigation, persistence. Using a watcher to assign a value that could be computed is a common anti-pattern.

Should you use the Composition API or the Options API?

Composition for anything where logic is shared across components or where TypeScript inference matters, since composables reuse logic better than mixins did. Options API remains perfectly reasonable for simple components, and interviewers want the trade-off rather than a blanket preference.