(1/12) How do you define watchers if you only want them to run on the client and not in SSR for a Vue 3 app?

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• Watchers run the same in SSR by default, so it's not possible to differentiate
• Use watchers in main.js for concurrency watchers only
• Gate them behind a check: if (typeof window !== 'undefined') or if (!import.meta.env.SSR) { watch(...) } so they skip SSR usage
• Use defineExpose for concurrency watchers

(2/12) How do you define watchers for an SSR-only property in Vue 3, for example onServerPrefetch data, if you want concurrency checks on the server?

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• Watchers do not run in SSR context typically, so concurrency watchers on the server are rarely used. You normally do synchronous or single-pass logic in SSR, or handle it in onServerPrefetch only
• No approach for concurrency watchers in SSR
• Use watchers in main.js for concurrency watchers
• Use defineProps for concurrency watchers

(3/12) Which environment variable do you typically check to detect if your Vue 3 app is running in production vs. development mode?

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• window.isProduction
• Vue 3 does not support environment variables
• process.env.DEBUG
• import.meta.env.MODE or process.env.NODE_ENV

(4/12) How do you define watchers for concurrency in a multi-root Vue 3 SFC if you intentionally have multiple top-level elements, each requiring separate concurrency logic?

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• Use watchers in main.js for concurrency watchers only
• Use defineProps for concurrency watchers
• Multiple roots do not affect watchers. The watchers are declared in setup or watchers array. You can watch whichever data or props you want, and define concurrency with onInvalidate. The number of root nodes is irrelevant to watchers
• Impossible to have multiple watchers if multiple roots exist

(5/12) How do you define watchers for concurrency if you have two different search fields in a single form and each must cancel its previous request in Vue 3?

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• Impossible to cancel multiple watchers
• Use watchers in main.js for concurrency watchers only
• Use defineProps for concurrency watchers
• Use watch(...) for each field separately, each with its own onInvalidate logic to cancel the prior request for that field

(6/12) In Vue 3, how can you define watchers for concurrency that handle user input across multiple text fields if each field triggers a separate API call, all of which can be canceled if the user changes input again?

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• Define separate watchers for each field, each using onInvalidate to cancel its own prior request. They do not block each other if they're separate watchers
• Use watchers in main.js for concurrency watchers only
• Impossible to have multiple watchers with concurrency logic
• Use defineExpose for concurrency watchers

(7/12) How does Vue 3 achieve better performance compared to Vue 2?

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• By removing the virtual DOM entirely
• Through a new compiler and proxy-based reactivity with tree-shaking friendly architecture
• It uses jQuery internally for DOM manipulation
• It removed all lifecycle hooks to speed up rendering

(8/12) How do you define watchers for concurrency if you want an advanced scenario where the same data field changes in two different parallel watchers in Vue 3, each potentially invalidating the other’s async operation?

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• Use watchers in main.js for concurrency watchers only
• Use defineProps for concurrency watchers only
• Impossible to define parallel watchers on one field
• You can define multiple watchers referencing the same field, each with onInvalidate. If the user toggles or reassigns the field, both watchers might try to cancel each other’s tasks. You must coordinate carefully or unify them in a single callback to avoid confusion

(9/12) If you want to lazy-load a component in a <script setup> block (not via the router), how might you do it?

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• Use watchers for the import statement
• You cannot lazy-load components in script setup
• Add a <script lazy> block instead of <script setup>
• Use defineAsyncComponent(() => import('./MyComp.vue')) in the top-level script, then reference it in the template

(10/12) How do you define watchers in a Vue 3 app if you only want them to run in dev mode for debugging concurrency or data flow?

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• Use defineProps for concurrency watchers
• No approach to conditionally define watchers for dev only
• Use watchers in main.js for concurrency watchers only
• Wrap watchers in a condition like if (import.meta.env.DEV) { watch(..., ...) }. Then they exist only in dev. Alternatively, remove them from production build code with environment checks

(11/12) Which statement about watchers is accurate if you define them both in the child and parent referencing the same data in Vue 3?

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• They merge watchers into one callback
• Impossible to have child and parent watchers on the same data
• They run in some sequence determined by the reactivity system. Both watchers will see changes, but no strict guaranteed ordering unless you rely on flush mode differences
• Use watchers in main.js for concurrency watchers only

(12/12) How can you define watchers for concurrency that differentiate ephemeral route transitions in Vue 3 if you have transitions triggered by dynamic imports and local data changes simultaneously?

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• Use watchers in main.js for concurrency watchers only
• Use defineProps for concurrency watchers
• Use separate watchers for route changes vs. local data changes, each with distinct onInvalidate. Possibly rely on an effect scope if you want them to share cancellation logic
• Impossible to differentiate ephemeral transitions

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