What is Vue.js?

What is Vue.js?

Vue.js is a progressive JavaScript framework for building user interfaces and single-page applications. Created by Evan You in 2014, Vue distinguishes itself from React and Angular by being approachable: most developers can be productive in Vue within hours rather than weeks. The current major version is Vue 3 (released September 2020), which introduced the Composition API alongside the original Options API.

The word "progressive" in Vue's tagline matters. Unlike Angular (heavyweight framework, opinionated about everything) or React (lightweight library that requires assembling your own ecosystem), Vue is designed to scale with your needs. Drop a single <script> tag onto an HTML page to add reactive behavior to one widget. Or use the full Vue ecosystem (Vue Router, Pinia, Nuxt, Vite) to build a production SPA. The same framework supports both extremes.

The two APIs: Options vs. Composition

Options API (Vue 2 style, still supported in Vue 3)

Components are declared as objects with named sections (data, methods, computed, watch, lifecycle hooks):

export default {
  data() {
    return { count: 0 };
  },
  computed: {
    doubled() { return this.count * 2; }
  },
  methods: {
    increment() { this.count++; }
  }
}

Easy to teach, easy to read, but logic for one feature gets scattered across sections.

Composition API (Vue 3 default for new code)

Logic is organized by concern using setup() and reactive primitives (ref, reactive, computed, watch):

import { ref, computed } from 'vue';

export default {
  setup() {
    const count = ref(0);
    const doubled = computed(() => count.value * 2);
    const increment = () => count.value++;
    return { count, doubled, increment };
  }
}

Better for complex components and code reuse via composables (Vue's equivalent of React hooks). The <script setup> syntactic sugar makes it even more concise.

The Vue ecosystem (the parts that ship with the framework)

• Vue Router — official routing library. SPA navigation, route params, nested routes, lazy loading, route guards.
• Pinia — official state management (replaced Vuex in Vue 3). Type-safe, devtool-integrated, simpler API than Redux.
• Vite — Evan You's own dev server and build tool. Used as Vue's default since 2021. Sub-second hot module reload.
• Vue DevTools — browser extension for inspecting components, state, and events.
• Nuxt — meta-framework on top of Vue (Vue's equivalent of Next.js). SSR, file-based routing, auto-imports, built-in API routes.

Vue vs. React vs. Angular (the honest comparison)

Common Vue performance considerations

• v-for + v-if on the same element. Don't do it. v-if takes precedence in Vue 3, which means v-for doesn't even run when v-if is false (good for skipping but confusing). Better: wrap in a <template> with v-if or pre-filter the array.
• Watchers exploding in count. Each watch creates a reactivity dependency. Use watchEffect sparingly. Prefer computed when you can.
• Non-reactive deep data. If you have large data structures that don't need to be reactive (like a 10K-row table reference), use shallowRef or markRaw to skip Vue's proxy wrapping.
• Bundle size from the entire ecosystem. Vue Router + Pinia + a UI library + your code can hit 200KB+ gzipped quickly. Use Vite's bundle analyzer and lazy-load route components.
• Hydration mismatches in SSR. Server renders a slightly different DOM than client mounts. Check that your data is identical on both sides — common culprits are Date, random IDs, and feature flags.

Vue 2 vs. Vue 3 migration considerations

Vue 2 reached end-of-life on December 31, 2023. If you're still on Vue 2, start the migration now. Key breaking changes:

• Reactivity uses Proxy now instead of Object.defineProperty — more reliable, but means you can't reactively detect adding new properties.
• Multiple root nodes per component (fragments) are now allowed.
• Teleport API for rendering elsewhere in the DOM.
• Better TypeScript support throughout.
• filters were removed; use computed properties or methods instead.
• Several event APIs renamed ($listeners merged into $attrs).

The Vue migration build helps you upgrade incrementally rather than big-bang.

FAQ: Vue.js

Should I learn Vue or React in 2026?

If you have a job opportunity for one specifically, learn that one. Otherwise: React has more jobs but is harder; Vue is easier and growing fast outside the U.S. (especially Asia and Europe). Knowing one makes learning the other much faster.

Is Vue still actively maintained?

Yes, very active. Vue 3.4 was released in late 2023, 3.5 in 2024 with major reactivity improvements, and active work continues. Evan You started VoidZero in 2024 to commercialize and accelerate the entire Vue/Vite ecosystem.

Composition API or Options API?

For new projects in Vue 3, use the Composition API with <script setup>. It's better for code reuse, TypeScript support, and complex components. The Options API is still supported and fine for simpler components or teams already using it.

Can Vue do server-side rendering?

Yes — via Nuxt (full meta-framework) or Vue's own SSR APIs (more manual). Nuxt is the right choice for most production SSR apps.

Is Vue good for mobile apps?

Yes via NativeScript-Vue (compiles to native iOS/Android), Quasar (Vue-based hybrid framework), or Ionic Vue (web-tech-on-native). For pure-native, the React Native ecosystem is more mature.

How does Vue handle TypeScript?

Excellent in Vue 3. Define props with defineProps<{...}>(), use ref<Type>(), etc. The Composition API was designed with TypeScript in mind. The Options API has TypeScript support too but feels less natural.

How LoadFocus relates to Vue applications

Vue SPAs depend on JavaScript bundles being delivered quickly to users. Bundle size, render speed, and route-transition performance directly affect user experience. LoadFocus website speed testing validates your Vue app's Core Web Vitals from 30+ locations. Load testing validates that the API endpoints your Vue components call hold up under realistic concurrent traffic — particularly important for SPAs where one page can issue 10-30 API calls per route change.