Vue 3 best practices, common gotchas, and performance optimization.

Reactivity

• Accessing ref() values without .value in scripts → See ref-value-access
• Destructuring reactive() objects, losing reactivity → See reactive-destructuring
• Choosing between ref() and reactive() for state → See prefer-ref-over-reactive
• Accessing refs inside arrays and collections → See refs-in-collections-need-value
• Large objects or external library data overhead → See shallow-ref-for-performance
• Using nested refs in template expressions → See template-ref-unwrapping-top-level
• Comparing reactive objects with === operator → See reactivity-proxy-identity-hazard
• Library instances breaking in reactive state → See reactivity-markraw-for-non-reactive
• Expecting watchers to fire for each state change → See reactivity-same-tick-batching
• Integrating external state management libraries → See reactivity-external-state-integration
• Tracing unexpected re-renders and state updates → See reactivity-debugging-hooks
• Deriving state with watchEffect instead of computed → See reactivity-computed-over-watcheffect-mutations

Computed

• Computed getter is making API calls or mutations → See computed-no-side-effects
• Mutating computed values causes lost changes unexpectedly → See computed-return-value-readonly
• Computed property doesn't update when expected → See computed-conditional-dependencies
• Sorting or reversing arrays destroys original data → See computed-array-mutation
• Expensive operations running too frequently every render → See computed-vs-methods-caching
• Trying to pass arguments to computed properties → See computed-no-parameters
• Complex conditions bloating inline class bindings → See computed-properties-for-class-logic

Watchers

• Need to watch a reactive object property → See watch-reactive-property-getter
• Large nested data structures causing performance issues → See watch-deep-performance
• Async operations overwriting with stale data → See watch-async-cleanup
• Creating watchers inside async callbacks → See watch-async-creation-memory-leak
• Dependencies accessed after await not tracking → See watcheffect-async-dependency-tracking
• Need to access updated DOM in watchers → See watch-flush-timing
• Uncertain whether to use watch or watchEffect → See watch-vs-watcheffect
• Duplicating initial calls and watch callbacks → See watch-immediate-option
• Can't compare old and new values correctly → See watch-deep-same-object-reference
• Template refs appearing null or stale → See watcheffect-flush-post-for-refs

Components

• Prop values being changed from a child component → See props-are-read-only
• Parent can't access child ref data in script setup → See component-ref-requires-defineexpose
• Child component throws "component not found" error → See local-components-not-in-descendants
• Click listener doesn't fire on custom component → See click-events-on-components
• HTML template parsing breaks Vue component syntax → See in-dom-template-parsing-caveats
• Grandparent can't listen to grandchild emitted events → See component-events-dont-bubble
• Wrong component renders due to naming collisions → See component-naming-conflicts
• Distinguishing Vue components from native elements → See component-naming-pascalcase
• Parent styles don't apply to multi-root component → See multi-root-component-class-attrs
• Recursive component needs to reference itself → See self-referencing-component-name
• Bundle includes components that aren't used → See prefer-local-component-registration
• Tight coupling through component ref access → See prefer-props-emit-over-component-refs

Props & Emits

• Boolean prop not parsing as expected → See prop-boolean-casting-order
• Composable doesn't update when props change → See prop-composable-reactivity-loss
• Variables referenced in defineProps cause errors → See prop-defineprops-scope-limitation
• Destructured props not updating watchers → See prop-destructured-watch-getter
• Prop validation needs component instance data → See prop-validation-before-instance
• Component emits undeclared event causing warnings → See declare-emits-for-documentation
• defineEmits used inside function or conditional → See defineEmits-must-be-top-level
• defineEmits has both type and runtime arguments → See defineEmits-no-runtime-and-type-mixed
• Event name inconsistency in templates and scripts → See emit-kebab-case-in-templates
• Event payloads need validation during development → See emit-validation-for-complex-payloads
• Native event listeners not responding to clicks → See native-event-collision-with-emits
• Component event fires twice when clicking → See undeclared-emits-double-firing

Templates

• Rendering untrusted user content as HTML → See v-html-xss-security
• Filtering or conditionally hiding list items → See no-v-if-with-v-for
• List items disappearing or swapping state unexpectedly → See v-for-key-attribute
• Getting template compilation errors with statements → See template-expressions-restrictions
• Dynamic directive arguments not working properly → See dynamic-argument-constraints
• Functions in templates modifying data unexpectedly → See template-functions-no-side-effects
• v-else elements rendering unconditionally always → See v-else-must-follow-v-if
• Child components in loops showing undefined data → See v-for-component-props
• Array order changing after sorting or reversing → See v-for-computed-reverse-sort
• Getting off-by-one errors with range iteration → See v-for-range-starts-at-one
• Performance issues with filtered or sorted lists → See v-for-use-computed-for-filtering
• "Cannot read property of undefined" runtime errors → See v-if-null-check-order
• Deciding between v-if and v-show for conditionals → See v-if-vs-v-show-performance
• v-show or v-else not working on template elements → See v-show-template-limitation

Template Refs

• Ref becomes null when element is conditionally hidden → See template-ref-null-with-v-if
• Ref array indices don't match data array in loops → See template-ref-v-for-order
• Refactoring template ref names breaks silently in code → See use-template-ref-vue35

Forms & v-model

• Initial form values not showing when using v-model → See v-model-ignores-html-attributes
• Textarea content changes not updating the ref → See textarea-no-interpolation
• iOS users cannot select dropdown first option → See select-initial-value-ios-bug
• Parent and child components have different values → See define-model-default-value-sync
• Need to handle v-model modifiers in child → See definemodel-hidden-modifier-props
• Object property changes not syncing to parent → See definemodel-object-mutation-no-emit
• Need to use updated value immediately after change → See definemodel-value-next-tick
• Real-time search/validation broken for Chinese/Japanese input → See v-model-ime-composition
• Number input returns empty string instead of zero → See v-model-number-modifier-behavior
• Migrating Vue 2 components to Vue 3 → See v-model-vue3-breaking-changes
• Custom checkbox values not submitted in forms → See checkbox-true-false-value-form-submission

Events & Modifiers

• Chaining multiple event modifiers produces unexpected results → See event-modifier-order-matters
• Need to handle same event only one time → See event-once-modifier-for-single-use
• Keyboard shortcuts fire with unintended modifier combinations → See exact-modifier-for-precise-shortcuts
• Keyboard shortcuts don't fire with system modifier keys → See keyup-modifier-timing
• Using left-handed mouse or non-standard input devices → See mouse-button-modifiers-intent
• Preventing default browser action and scroll performance together → See no-passive-with-prevent

Lifecycle

• Lifecycle hooks don't execute asynchronously → See lifecycle-hooks-synchronous-registration
• DOM access fails before component mounts → See lifecycle-dom-access-timing
• Memory leaks from unremoved event listeners → See cleanup-side-effects
• SSR rendering differs from client hydration → See lifecycle-ssr-awareness
• Expensive operations slow performance drastically → See updated-hook-performance
• DOM reads return stale values after state changes → See dom-update-timing-nexttick

Slots

• Accessing child component data in slot content → See slot-render-scope-parent-only
• Mixing named and scoped slots together → See slot-named-scoped-explicit-default
• Using v-slot on native HTML elements → See slot-v-slot-on-components-or-templates-only
• Empty wrapper elements rendering unnecessarily → See slot-conditional-rendering-with-slots
• Scoped slot props lack TypeScript type safety → See slot-define-slots-for-typescript
• Rendering empty component slots without defaults → See slot-fallback-content-default-values
• Wrapper components breaking child slot functionality → See slot-forwarding-to-child-components
• Confused about which slot content goes where → See slot-implicit-default-content
• Expecting name property in scoped slot props → See slot-name-reserved-prop
• Choosing between renderless components and composables → See slot-renderless-components-vs-composables

Provide/Inject

• Injected values not updating when provider changes → See provide-inject-reactivity-not-automatic
• Calling provide after async operations fails silently → See provide-inject-synchronous-setup
• String keys collide in large applications → See provide-inject-symbol-keys
• Tracing where provided values come from → See provide-inject-debugging-challenges
• Multiple components share same default object → See provide-inject-default-value-factory
• State mutations scattered across components → See provide-inject-mutations-in-provider
• Passing props through many component layers → See avoid-prop-drilling-use-provide-inject

Attrs

• Both internal and fallthrough event handlers execute → See attrs-event-listener-merging
• Accessing hyphenated attributes in JavaScript code → See attrs-hyphenated-property-access
• Watching fallthrough attributes for changes with watch() → See attrs-not-reactive
• Explicit attributes overwritten by fallthrough values → See fallthrough-attrs-overwrite-vue3
• Attributes applying to wrong element in wrappers → See inheritattrs-false-for-wrapper-components

Composables

• Composable has unexpected side effects affecting external state → See composable-avoid-hidden-side-effects
• Composable called outside setup context or asynchronously → See composable-call-location-restrictions
• Building complex logic from smaller focused composables → See composable-composition-pattern
• Inconsistent composable names or destructuring loses reactivity → See composable-naming-return-pattern
• Composable has many optional parameters or confusing argument order → See composable-options-object-pattern
• Need to prevent uncontrolled mutations of composable state → See composable-readonly-state
• Composable reactive dependency not updating when input changes → See composable-tovalue-inside-watcheffect
• Unsure whether logic belongs in composable or utility function → See composable-vs-utility-functions

Composition API

• Optimizing production bundle size and performance → See composition-api-bundle-size-minification
• Composition API code becoming scattered and hard to maintain → See composition-api-code-organization
• Fixing naming conflicts and unclear data origins in mixins → See composition-api-mixins-replacement
• Applying functional patterns incorrectly to Vue state → See composition-api-not-functional-programming
• Gradually migrating large Options API codebase → See composition-api-options-api-coexistence
• Lifecycle hooks failing silently after async operations → See composition-api-script-setup-async-context
• Coming from React, over-engineering Vue patterns unnecessarily → See composition-api-vs-react-hooks-differences
• Parent component refs unable to access exposed properties → See define-expose-before-await

Directives

• Storing state across directive hooks → See directive-arguments-read-only
• Applying custom directives to Vue components → See directive-avoid-on-components
• Creating intervals or event listeners in directives → See directive-cleanup-in-unmounted
• Simplifying directives with identical behavior → See directive-function-shorthand
• Using custom directives in script setup → See directive-naming-v-prefix
• Choosing between custom and built-in directives → See directive-prefer-declarative-templating
• Deciding between directives and components → See directive-vs-component-decision
• Migrating Vue 2 directives to Vue 3 → See directive-vue2-migration-hooks

Transitions

• Wrapping multiple elements or components in transitions → See transition-single-element-slot
• Transitioning between same element types without animation → See transition-key-for-same-element
• Using JavaScript animations without calling done callback → See transition-js-hooks-done-callback
• Animating lists with TransitionGroup without unique keys → See transition-group-key-requirement
• Performance problems with janky list animations → See transition-animate-transform-opacity
• Move animations failing on inline list elements → See transition-group-flip-inline-elements
• List items jumping instead of smoothly animating → See transition-group-move-animation-position-absolute
• Vue 2 to Vue 3 transition layout breaks unexpectedly → See transition-group-no-default-wrapper-vue3
• Trying to sequence list animations with mode prop → See transition-group-no-mode-prop
• Creating cascading delays for list item animations → See transition-group-staggered-animations
• Overlapping elements or layout jumping during transitions → See transition-mode-out-in
• Nested transition animations cutting off prematurely → See transition-nested-duration
• Reusable transition components with scoped styles breaking → See transition-reusable-scoped-style
• RouterView transitions unexpectedly animating on page load → See transition-router-view-appear
• Mixing CSS transitions and animations causing timing issues → See transition-type-when-mixed
• Component cleanup not firing during fast transition replacements → See transition-unmount-hook-timing

Animation

• Need to animate elements staying in DOM → See animation-class-based-technique
• Animations not triggering on content changes → See animation-key-for-rerender
• Building interactive animations with user input → See animation-state-driven-technique
• Animating list changes causing noticeable lag → See animation-transitiongroup-performance

KeepAlive

• Using KeepAlive without proper cache limits or cleanup → See keepalive-memory-management
• KeepAlive include/exclude props not matching cached components → See keepalive-component-name-requirement
• Need to programmatically remove component from KeepAlive cache → See keepalive-no-cache-removal-vue3
• Users see stale cached content when expecting fresh page data → See keepalive-router-fresh-vs-cached
• Child components mount twice with nested Vue Router routes → See keepalive-router-nested-double-mount
• Memory grows when combining KeepAlive with Transition animations → See keepalive-transition-memory-leak
• Dynamic component state resets when switching between them → See dynamic-components-with-keepalive

Async Components

• Setting up Vue Router route component loading → See async-component-vue-router
• Async component options ignored by parent Suspense → See async-component-suspense-control
• Network failures or timeouts loading components → See async-component-error-handling
• Improving Time to Interactive with SSR apps → See async-component-hydration-strategies
• Template refs undefined after component reactivation → See async-component-keepalive-ref-issue
• Loading spinner flashing on fast networks → See async-component-loading-delay

Render Functions

• Render function from setup doesn't update reactively → See rendering-render-function-return-from-setup
• Same vnode appearing multiple times in tree → See render-function-vnodes-must-be-unique
• Rendering lists in render functions without keys → See render-function-v-for-keys-required
• Implementing .stop, .prevent in render functions → See render-function-event-modifiers
• Two-way binding on components in render functions → See render-function-v-model-implementation
• Using string names for components in render functions → See rendering-resolve-component-for-string-names
• Accessing vnode internals like el or shapeFlag → See render-function-avoid-internal-vnode-properties
• Creating simple stateless presentational components → See render-function-functional-components
• Applying custom directives in render functions → See render-function-custom-directives
• Excessive rerenders from watchers or deep watchers → See rendering-excessive-rerenders-watch-vs-computed
• Choosing render functions over templates → See rendering-prefer-templates-over-render-functions
• Migrating Vue 2 render functions to Vue 3 → See rendering-render-function-h-import-vue3
• Passing slot content to h() incorrectly → See rendering-render-function-slots-as-functions
• Understanding Vue's vdom optimization blocks → See rendering-understand-vdom-block-structure

Teleport

• Teleport target element not found in DOM → See teleport-target-must-exist
• Teleported content breaks SSR hydration → See teleport-ssr-hydration
• Modal breaks with parent CSS transforms → See teleport-css-positioning-issues
• Content needs different layout on mobile → See teleport-disabled-for-responsive
• Unsure if props/events work through teleport → See teleport-logical-hierarchy-preserved
• Multiple modals targeting same container → See teleport-multiple-to-same-target
• Scoped styles not applying to teleported content → See teleport-scoped-styles-limitation

Suspense

• Need to handle async errors from Suspense components → See suspense-no-builtin-error-handling
• Want to track Suspense loading states programmatically → See suspense-events-for-state-tracking
• Planning Suspense usage in production applications → See suspense-experimental-api-stability
• Fallback not showing when content changes → See suspense-fallback-not-immediate-on-revert
• Nesting Suspense components together → See suspense-nested-suspensible-prop
• Combining Suspense with Router, Transition, KeepAlive → See suspense-nesting-order-with-router
• Nested async component not showing loading indicator → See suspense-revert-only-on-root-change
• Multiple async components in single Suspense → See suspense-single-child-requirement
• Using Suspense with server-side rendering → See suspense-ssr-hydration-issues

TypeScript

• Declaring props with TypeScript in composition API components → See ts-defineprops-type-based-declaration
• Providing default values to mutable prop types → See ts-withdefaults-mutable-factory-function
• Typing reactive state with ref unwrapping concerns → See ts-reactive-no-generic-argument
• Accessing DOM elements after component mounts → See ts-template-ref-null-handling
• Typing refs to child Vue components → See ts-component-ref-typeof-instancetype
• Using custom directives with TypeScript support → See ts-custom-directive-type-augmentation
• Declaring component events with full type safety → See ts-defineemits-type-based-syntax
• Handling optional boolean props in TypeScript → See ts-defineprops-boolean-default-false
• Using imported types safely in defineProps → See ts-defineprops-imported-types-limitations
• Handling DOM events with strict TypeScript checking → See ts-event-handler-explicit-typing
• Sharing data between components with type safety → See ts-provide-inject-injection-key
• Storing Vue components in reactive state → See ts-shallowref-for-dynamic-components
• Working with union types in Vue templates → See ts-template-type-casting

SSR

• User data leaking between server requests → See state-ssr-cross-request-pollution
• HTML differs between server and client renders → See ssr-hydration-mismatch-causes
• Code runs on both server and browser environments → See ssr-platform-specific-apis
• Custom directives not displaying on server-rendered HTML → See ssr-custom-directive-getssrprops

Performance

• Many list items re-rendering unnecessarily during state changes → See perf-props-stability-update-optimization
• Rendering hundreds or thousands of items causing DOM performance issues → See perf-virtualize-large-lists
• Static content re-evaluated on every parent component update → See perf-v-once-v-memo-directives
• List performance degrading from deeply nested component structure → See perf-avoid-component-abstraction-in-lists
• Computed properties returning objects triggering effects unexpectedly → See perf-computed-object-stability
• Page load metrics suffering from client-side JavaScript execution delay → See perf-ssr-ssg-for-page-load

SFC (Single File Components)

• Trying to use named exports from component script blocks → See sfc-named-exports-forbidden
• Starting a Vue project with a build setup → See sfc-recommended-for-build-projects
• Styling child component elements with scoped CSS → See sfc-scoped-css-child-component-styling
• Styling content added dynamically with v-html → See sfc-scoped-css-dynamic-content
• Optimizing scoped CSS selector performance → See sfc-scoped-css-performance
• Styling content passed through component slots → See sfc-scoped-css-slot-content
• Variables not updating in template after changes → See sfc-script-setup-reactivity
• Organizing component template, logic, and styles → See sfc-separation-of-concerns-colocate
• Binding inline styles with property names → See style-binding-camelcase
• Building Tailwind classes with string concatenation → See tailwind-dynamic-class-generation

Plugins

• Debugging why global properties cause naming conflicts → See plugin-global-properties-sparingly
• Plugin not working or inject returns undefined → See plugin-install-before-mount
• Global properties not available in setup function → See plugin-prefer-provide-inject-over-global-properties
• Creating a new Vue plugin from scratch → See plugin-structure-install-method
• Preventing collisions between multiple plugins → See plugin-symbol-injection-keys
• Global properties missing TypeScript autocomplete support → See plugin-typescript-type-augmentation

App Configuration

• App configuration methods not working after mount call → See configure-app-before-mount
• Need to chain app configuration methods after mount → See mount-return-value
• Vue only controlling specific page sections → See multiple-app-instances
• Migrating dynamic component registration to Vite → See dynamic-component-registration-vite