(1/20) If you have watchers referencing multiple data fields in a single callback in Vue 3, how do you ensure you only do a certain action if BOTH fields have changed, not just one?

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• Use defineProps for concurrency watchers
• Use watchers in main.js for concurrency watchers only
• No approach to require both changes simultaneously
• Use watch(() => [fieldA.value, fieldB.value], ([newA, newB], [oldA, oldB]) => { if(newA !== oldA && newB !== oldB) { ... } })

(2/20) Which technique can you use to rename the default 'modelValue' prop and 'update:modelValue' event in Vue 3 if you want a custom v-model name, without losing watchers or concurrency logic?

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• No approach to rename v-model prop/event
• Use watchers in main.js for concurrency watchers only
• Use defineProps for concurrency watchers
• Use custom v-model binding. For example, <Child v-model:custom="value" => props: { custom: ... }, emits: ['update:custom']. Then watchers referencing props.custom still work

(3/20) Which statement about globalProperties in a Vue 3 app is accurate?

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• No such property exists in Vue 3
• It allows you to define app.config.globalProperties.myProp to be accessible in Options API as this.$myProp
• It automatically merges watchers with directives
• It replaces watchers for all components

(4/20) Which approach in Vue 3 is best if you only need to run a callback after all child components have updated in a parent after reactive data changes?

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• Use nextTick(() => { ... }) inside onUpdated or watchers with flush: 'post'
• No approach for waiting child updates
• Use watchers with flush: 'pre'
• Use defineProps to track children

(5/20) How can you force Vue 3 to re-render a component if the reactivity system doesn’t detect any changes in your data (edge case)?

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• Change the name of the component file
• Use forceUpdate() from the old Vue 2 API
• Vue 3 does not allow forcing re-renders
• Use a 'key' attribute that changes to trigger a new render

(6/20) When might you define a watch with { immediate: true, deep: true } in Vue 3?

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• It is forbidden by Vue 3 for performance reasons
• If you want the callback to fire on component creation once and for any deeply nested changes in the watched object
• No scenario requires both immediate and deep
• Immediate watchers only apply to arrays, not objects

(7/20) Which advanced SSR optimization might you apply in Vue 3 if certain components produce large static subtrees but occasionally update one small portion client-side?

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• Impossible to partially hydrate static subtrees
• Use defineProps for concurrency watchers
• Use watchers in concurrency watchers mode only
• You can break out that small portion into a separately hydrated dynamic region while marking the rest with v-once or static hoisting, or investigate partial hydration proposals to skip re-hydrating the entire subtree

(8/20) Which approach might you take if your watchers for concurrency in a child component rely on parent route data that changes, but you also want the parent to handle concurrency first in Vue 3?

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• Use watchers in main.js for concurrency watchers only
• Use defineExpose for concurrency watchers
• No approach to coordinate watchers between parent and child
• One approach is to do concurrency watchers in the parent to finalize or transform the data before passing it as props to the child. The child might have minimal watchers if needed. Or define a global route guard. There's no forced sequence unless you design it that way

(9/20) How do you create a custom asynchronous validator for a prop in Vue 3, ensuring the prop data is valid after an API check?

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• Use a keep-alive component for validation
• Use defineProps() with an async validator or manually handle validation in the parent before passing the prop
• Vue 3 does not support asynchronous prop validation by default
• Use watchEffect for that prop to re-render if invalid

(10/20) Which statement about watchers in Vue 3 with { flush: 'sync' } is correct?

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• It’s identical to watchEffect
• sync watchers only work for array references
• It forces the watcher to run synchronously as soon as the tracked source changes, before the DOM update or other watchers
• The watcher callback is invoked immediately, blocking the event loop until it finishes

(11/20) When might you need to use the globalProperties object in Vue 3?

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• To patch the reactivity system manually
• To define a property or function accessible as this.$myProp in every component, similar to Vue 2’s prototype
• To globally register watchers
• To remove pinned dependencies from the router

(12/20) Which approach is preferred for deeply nested data in Vue 3 if you do not need to track changes at every nested level?

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• Rewrite the entire data structure in watchers
• Vue 3 no longer supports nested objects
• Use shallowReactive or shallowRef for performance
• Use watchers on all nested properties

(13/20) How might you unify concurrency watchers across multiple Pinia stores if the user can trigger changes in multiple modules that overlap in time?

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• Use watchers in main.js for concurrency watchers only
• Create a top-level effect scope or a custom concurrency manager that each store watchers references. If a new event conflicts, the manager can call the onInvalidate or stop methods for watchers in multiple stores
• Impossible to unify concurrency watchers across multiple stores
• Use defineProps for concurrency watchers

(14/20) How would you handle an async operation in a composable so that multiple components using that composable do not trigger duplicate requests?

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• Store the async data in a shared reactive variable or a global store so it’s fetched once and reused
• Use watchEffect in each component to forcibly run the request every time
• Vue 3 disallows shared composables for async data
• Each component must create a new instance of the composable, so duplication is unavoidable

(15/20) What happens if you attempt to destructure props at the top of setup() in Vue 3 (e.g., const { title } = props) and then rely on reactivity changes?

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• title remains reactive, updating when props change
• Vue 3 forbids destructuring props in the setup function
• Vue re-reads props automatically in the destructured variables
• Destructuring breaks reactivity unless you manually reassign or use toRefs()

(16/20) Which approach helps with performance if you have many watchers on a large object in Vue 3, but only some fields are truly reactive or relevant?

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• Use defineExpose for concurrency watchers
• Use watchers in main.js for concurrency watchers only
• No approach to optimize watchers in Vue 3
• Use a shallowReactive or separate smaller reactive objects for just the fields needed, avoiding a full deep watch on the entire object

(17/20) What is the recommended way to define an app-wide error boundary in Vue 3, catching unhandled errors from any component?

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• Place onErrorCaptured in every single child component
• Watch for console.error events using watchers
• No official approach exists
• Use app.config.errorHandler for global error handling, or define an errorCaptured hook in the root component

(18/20) Which approach might you use to optimize an expensive computed property in Vue 3 that only updates under certain conditions?

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• Use watchEffect() instead of computed()
• Wrap the logic in a computed() and ensure it only depends on the necessary reactive sources
• Use shallowRef() to store the computed value
• Call the method in onMounted() to force it once and store results in data()

(19/20) Which Vue 3 feature can be used to create advanced animations that coordinate multiple transitions or reorder transitions in a more controlled way?

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• Use watchers on every frame
• Vue 3 removed support for advanced animations
• Use a global directive named v-animate
• Use the Transition and TransitionGroup components plus JavaScript transition hooks for fully customized animations

(20/20) Which statement about watchers is correct if you define watch(computedProperty, callback) for concurrency in Vue 3, referencing an async function in the callback?

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• No approach for concurrency with computed watchers
• Use watchers in main.js for concurrency watchers
• The callback can define onCleanup / onInvalidate to handle concurrency if a new change arrives mid-async call
• Use defineProps for concurrency watchers only

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