Lifecycle Hooks Interview Questions

Lifecycle hooks are special methods that allow executing code at specific stages of a component's life. Include creation, mounting, updating, and destruction phases. Available in both Options API and Composition API.

created runs after instance is created, reactive data is set up. Can access reactive data and events. Cannot access DOM/this.$el. Good for initial data fetching. Composition API equivalent: onCreated.

mounted executes when component is mounted to DOM. Can access DOM elements and refs. Good for DOM manipulations and third-party library initialization. Composition API: onMounted.

updated runs after data changes and DOM updates. Can access updated DOM. Should avoid changing state to prevent infinite loops. Composition API: onUpdated.

unmounted executes when component is removed from DOM. Used for cleanup (removing event listeners, canceling timers). All directives unbound, watchers stopped. Composition API: onUnmounted.

beforeCreate runs before instance initialization. Cannot access reactive data or events. Used for plugin initialization. Composition API setup() runs before this hook.

beforeMount executes before DOM mounting begins. Template is compiled but not mounted. Cannot access DOM elements. Composition API: onBeforeMount.

beforeUpdate runs before DOM updates after data change. Can access old DOM state. Good for saving state before update. Composition API: onBeforeUpdate.

beforeUnmount executes before component unmounting starts. Component still fully functional. Good for cleanup initialization. Composition API: onBeforeUnmount.

Composition API uses on* prefixed functions for lifecycle hooks. Must be called synchronously in setup(). Support multiple calls. Return cleanup functions.

Use async/await or promises. Handle loading states. Support error handling. Implement cleanup for async operations. Consider component lifecycle.

Return cleanup function from setup hooks. Remove event listeners. Clear timers. Cancel subscriptions. Handle resource cleanup.

activated and deactivated hooks for cached components. Handle component activation. Support cache lifecycle. Implement caching strategies.

Use errorCaptured hook or try/catch. Handle error states. Support error recovery. Implement error boundaries. Handle error reporting.

Mixin hooks merge with component hooks. Handle hook ordering. Support hook composition. Implement mixin strategies.

Test hook execution order. Handle async testing. Support component mounting. Implement test utilities. Handle test scenarios.

Handle loading states. Support error states. Implement loading component. Handle async lifecycle. Support component loading.

Use Vue Devtools. Handle hook debugging. Support logging. Implement debugging strategies. Handle hook inspection.

Minimize hook operations. Handle heavy computations. Support performance optimization. Implement efficient patterns.

Create complex hook systems. Handle advanced scenarios. Support pattern composition. Implement advanced strategies.

Compose multiple hooks. Handle hook dependencies. Support hook reuse. Implement composition patterns.

Create hook-based plugins. Handle plugin lifecycle. Support plugin options. Implement plugin patterns.

Implement secure hook patterns. Handle sensitive operations. Support security measures. Implement security strategies.

Track hook execution. Handle performance monitoring. Support debugging tools. Implement monitoring strategies.

Design scalable hook systems. Handle hook organization. Support architecture patterns. Implement design principles.

Create comprehensive documentation. Generate API docs. Support example usage. Implement documentation systems.

Implement deployment strategies. Handle environment configuration. Support production optimization. Implement deployment patterns.

Create comprehensive test suites. Handle integration testing. Support unit testing. Implement test strategies.

Implement version updates. Handle migration strategies. Support backwards compatibility. Implement migration patterns.