Vue.js Answers

Basic Vue.js Answers

#	Question	Answer	Examples	Comparison to ReactJS
1	What is Vue.js?	A progressive JavaScript framework for building user interfaces	Developed by Evan You, known for its ease of use and flexibility	Both are JavaScript frameworks/libraries for building UIs. Vue is often considered easier to learn initially, especially for those with traditional HTML/CSS/JS backgrounds.
2	What is the purpose of Vue.js?	Building reusable UI components and managing application state	Creating single-page applications (SPAs), interactive web interfaces	Both focus on component-based architecture. Vue uses HTML-based templates; React uses JSX (JavaScript XML).
3	What is a Component?	A fundamental building block of a Vue application; a reusable piece of UI	A .vue file containing <template>, <script>, and <style> sections	Both use components. Vue uses Single File Components (SFCs) which bundle template, script, and style in one file. React typically uses separate files for each.
4	How do you create a simple component?	Define a JavaScript object with options API (data, methods, props)	<template><h1>Hello, {{ name }}</h1></template> <script> export default { props: ['name'] }; </script>	Vue uses HTML-based templates; React uses JSX. Both are compiled into similar function calls by build tools.
5	What are Props?	Data passed down from a parent component to a child component	<Child name="Alice" /> (name is a prop)	Both use props for passing data down. Vue's props are defined explicitly in the component's options. React's props are passed as function arguments.
6	What is State?	Data that is managed by a component and can change over time (internal)	data() { return { count: 0 }; } (Options API) or const count = ref(0); (Composition API)	Both manage component state. Vue uses data() function (Options API) or ref/reactive (Composition API). React uses useState hook.
7	How do you handle events in Vue?	Using the v-on directive (or its shorthand @)	<button @click="handleClick">Click Me</button>	Both use event handling. Vue uses directives (v-on: or @); React uses event handlers passed as props (onClick).
8	What is the v-if directive?	Conditionally renders an element based on a condition	<div v-if="isVisible">Visible</div>	Similar to React's conditional rendering logic.
9	How do you iterate over lists in Vue?	Using the v-for directive	<ul><li v-for="item in items" :key="item.id">{{ item.name }}</li></ul>	Similar to React's map() method. Vue uses v-for with :key; React uses map() with a key prop.
10	What is the v-model directive?	Two-way data binding on form elements	<input v-model="message">	Vue's built-in directive for two-way form binding. React typically requires explicit value prop and onChange handler.

Intermediate Vue.js Answers

#	Question	Answer	Examples	Comparison to ReactJS
1	What is the Options API?	The traditional way to define components using an object with options like data, methods, computed	export default { data() { ... }, methods: { ... } }	More similar to class components in React (though syntax is different).
2	What is the Composition API?	A newer way to structure component logic using setup() function and reactive primitives (ref, reactive)	import { ref } from 'vue'; export default { setup() { const count = ref(0); return { count }; } }	More similar to React Hooks (useState, useEffect). Allows better code organization and reuse.
3	What is ref() in the Composition API?	Creates a reactive reference to a primitive value; needs to be accessed with .value	const count = ref(0); count.value++;	Similar to React's useState for primitive values.
4	What is reactive() in the Composition API?	Creates a reactive proxy object; allows direct access to properties	const state = reactive({ count: 0 }); state.count++;	Similar to React's useState for objects/arrays.
5	What is computed()?	Creates a reactive property based on other reactive state; caches results	const doubledCount = computed(() => count.value * 2);	Similar to React's useMemo.
6	What is watch()?	Observes a reactive property or source and runs a callback when it changes	watch(count, (newValue, oldValue) => { ... });	Similar to React's useEffect with dependency arrays.
7	What are Lifecycle Hooks?	Functions that are called at specific stages of a component's life (e.g., mounted, updated)	onMounted(() => { ... }); (Composition API), mounted() { ... } (Options API)	Similar to React's lifecycle methods (class components) or useEffect (functional components).
8	What is Vue Router?	The official routing library for Vue.js	createRouter, createWebHistory, ,	Similar to React Router.
9	What is Pinia?	The official state management library for Vue.js (recommended for Vue 3)	defineStore, useStore, state, getters, actions	Similar to Redux or Zustand in React.
10	What is Vuex?	The previous official state management library for Vue.js (often used in Vue 2)	createStore, state, getters, mutations, actions, modules	Similar to Redux.
11	What are Slots?	Placeholders in a component's template where content can be injected by the parent	(default), (named)	Similar to React's children.
12	What is the difference between v-if and v-show?	v-if conditionally creates/removes the element; v-show toggles the CSS display property	v-if is better for less frequent changes; v-show is better for frequent toggling.	Similar to React's conditional rendering using if/else or ternary operators vs. conditional CSS display.
13	How do you pass data from child to parent?	Using custom events ($emit)	emit('my-event', payload) and parent listens @my-event="handleEvent".	Similar to React's passing callbacks down as props.
14	What is a Transition Component?	A built-in component for adding CSS transitions and animations to elements	...	Similar to React's CSS transitions/animations or libraries like react-transition-group.
15	What is a Global API?	A component that is available anywhere in the application	app.component('MyGlobalComponent', MyGlobalComponent)	Less common in modern React; components are typically imported and used locally.

Advanced Vue.js Answers

#	Question	Answer	Examples	Comparison to ReactJS
1	What are Composables?	Functions that encapsulate reusable stateful logic using the Composition API	function useCounter() { const count = ref(0); ... return { count, increment }; }	Similar to custom React Hooks (e.g., useFetch, useLocalStorage).
2	What is Teleport?	Allows part of a component's template to be rendered in a different location in the DOM (e.g., modals)	<Teleport to="#modal-root"> <MyModal /> </Teleport>	Similar to React's createPortal.
3	What is Suspense?	A built-in component for handling asynchronous setup (e.g., lazy loading components)	<Suspense fallback="<div>Loading...</div>"><MyAsyncComponent /></Suspense>	Similar to React's Suspense used with React.lazy.
4	What is the difference between v-if and v-for?	v-if has higher priority than v-for when both are used on the same element (use <template> to separate them)	<template v-for="item in items"><li v-if="item.isActive">{{ item.name }}</li></template>	Similar to React, you generally need to keep them separate or use conditional logic within the map call.
5	What is the difference between v-model.lazy and v-bind/ v-on?	v-model.lazy updates the data only on change event (or blur) instead of input event	<input v-model.lazy="message">	Similar to React using onChange handlers that only update state on specific events (e.g., blur or debounce).
6	What is provide / inject?	A way to pass data down to any descendant component deep in the component tree without prop drilling	Parent: provide('theme', this.theme); Child: const theme = inject('theme');	Similar to React's Context API (Provider / useContext).
7	What are Mixins?	A way to share reusable functionality across components (less common now with Composition API)	export default { mixins: [myMixin] };	Similar to React's Higher-Order Components (HOCs) or custom Hooks. Mixins can lead to naming conflicts and unclear property origins.
8	What is the purpose of script setup?	A syntax sugar for the Composition API components, reducing boilerplate code	<script setup> import { ref } from 'vue'; const count = ref(0); </script>	A more concise way to write Composition API components.
9	What is createApp (Vue 3)?	The entry point for creating a Vue 3 application instance	import { createApp } from 'vue'; const app = createApp(App); app.mount('#app');	Similar to ReactDOM.createRoot in React 18+.
10	What is the reactivity system in Vue 3?	Uses Proxies to track changes to data more efficiently than ObjectdefineProperty	ref and reactive are the core reactive primitives.	Similar to React's state management using useState.
11	What is a render function?	An alternative to templates for defining components using JavaScript code	render() { return h('div', {}, 'Hello'); }	Similar to React's JSX or React.createElement().
12	What is the difference between Vue 2 and Vue 3?	Vue 3 introduced Composition API, Proxy-based reactivity, better TypeScript support, Teleport, Suspense, etc.	Vue 3 generally offers better performance, smaller bundle size, and more flexible component structure.
13	How does the event system work in Vue.js?	Relies on the browser's native DOM events system, often using a synthetic event delegation		Similar to React's use of browser events and synthetic event system.
14	What are the benefits of the Composition API?	Better code organization, reusability, improved TypeScript inference, avoids this context issues		Similar to the benefits of React Hooks.
15	What are the drawbacks of the Composition API?	Steeper initial learning curve compared to Options API, can be less intuitive for beginners	Requires understanding of ref, reactive, setup, etc.