Deep Dive into Vue.js 3 Component Architecture

Anton Ioffe - December 29th 2023 - 11 minutes read

Welcome to the forefront of Vue.js 3, where the art of component design is being reimagined and refined. As we delve into the depths of this progressive JavaScript framework, you, the seasoned developer, will be guided through the transformative journey from the Options API to the potent Composition API, unraveling the nuanced world of state management, and peering into the interplay of stateless and stateful components. With an eye towards efficiency, we'll dissect the veins of communication and state across the component landscape before scaling the peaks of performance optimization. Together, we'll explore sophisticated strategies and best practices that promise to elevate your Vue.js 3 applications to new heights of excellence—a blueprint for the future of web development awaits.

Rethinking Component Design in Vue.js 3

Vue.js has always been recognized for its elegant and simple approach to building web interfaces through a harmonious integration of HTML, CSS, and JavaScript within single-file components. The initial representation, leveraging the Options API, was designed to categorize the component's properties by their functionality—data, methods, computed properties, and lifecycle hooks, among others. This convention promoted a clear structure, making it straightforward for developers to adopt and reason about their components. However, as applications grew in complexity, limitations emerged. The tight coupling within these grouped concerns posed challenges for effective code organization and reuse.

With the advent of Vue.js 3, we're witnessing a strategic shift that addresses the shortcomings of the earlier paradigm—ushering in a period of more granular and modular component structures. The underlying goal is to offer developers the ability to encapsulate and manage stateful logic more effectively. Thus, the Composition API is introduced, representing a significant shift from the Options API. It's not a full departure but rather an augmentation that provides developers with a new way to define and compose reactive state and logic. This compositional approach encourages developers to define a component’s reactive properties and functions as logically grouped sets, thus facilitating more flexible and maintainable codebases.

The Composition API shines in scenarios demanding a higher degree of abstraction and reusability. Components may now express their features as composable functions that can be imported and used across multiple components. This shift not only eradicates the common barriers to logic reuse encountered in large Vue applications but also mitigates potential name collisions—a testament to its improved design over mixin patterns. With reactivity scoped within setup functions and reactive references made more explicit, state management within components transitions to become more declarative and intentional.

In understanding the evolution of Vue.js components, we must also acknowledge the conscientious efforts made to ensure backward compatibility. Vue.js 3’s design preserves the use of the Options API, allowing for gradual migration and an inclusive approach for codebases of diverse sizes and complexities. This duality in design affirms Vue.js's commitment to a progressive enhancement strategy, in which the new Composition API operates not as a replacement but as a sophisticated supplement to the developer's toolkit.

At its core, the move towards the Composition API in Vue.js 3 is a testament to the framework's maturity. It's a response to the collective experience of the community and a reflection of the need for scalable and maintainable solutions in modern web development. The framework’s evolution articulates its inherent adaptability and resilience, demonstrating how embracing change can lead to a more robust and versatile approach to crafting web applications. As developers, we are called to recalibrate our understanding of component design within Vue, leveraging the tools at our disposal to craft cleaner, more efficient, and ultimately more powerfully abstracted code architectures.

Composition API: A New Paradigm for Vue Components

Vue.js 3's Composition API ushers in a nuanced era for component construction by encouraging a function-based approach to managing state and logic. This enables developers to architect their Vue applications with enhanced granularity in reactivity by defining 'composable' functions. These functions can encapsulate all the reactive essentials — references, computed values, and life-cycle hooks — into discrete, reusable units that can greatly elevate the modularity of application design.

Composability in this context is vital as it allows for distinct segments of functionality to be maintained and tested independently. Consider a scenario where we manage a user's permissions within an application. With a composable function, we can abstract this logic as follows:

import { ref, computed } from 'vue';

function usePermissions(user) {
    const permissions = ref([]);

    const hasPermission = (permission) => permissions.value.includes(permission);

    const isAdmin = computed(() => hasPermission('admin'));

    // Fetching user permissions from an API
    function fetchPermissions() {
        // replace with actual API call to fetch permissions
        permissions.value = user.value.permissions;

    // initially fetch user permissions

    return { permissions, hasPermission, isAdmin, fetchPermissions };

Efforts to consolidate related reactive data become particularly cogent when employing the Composition API. Developers can now structure their reactive data along with specific domain logic within their components, improving the signal-to-noise ratio in their codebase. The focus on domain-centric coding not only aligns logic cohesively but also bolsters the developer's ability to track and manage state changes within the system effectively.

However, with this functional harmony comes the responsibility to mindfully structure these compositions. To ensure reactivity is preserved when refactoring data into composable functions, one should employ the reactive primitives provided by Vue 3 diligently. Here’s how reactive state can be exposed and consumed by a component:

import { reactive, toRefs } from 'vue';
import { usePermissions } from './usePermissions';

function setup() {
    const user = reactive({ id: '123', name: 'Jane Doe', permissions: ['user'] });

    const { isAdmin, fetchPermissions } = usePermissions(toRefs(user));

    // ... other composable functions and logic

    return { user, isAdmin, fetchPermissions };

In the declarative gestalt of the Composition API, developers are not simply wiring up state and UI — they are curating the flow of reactivity within their applications. Being judicious about what is exposed through composable functions permits a more explicit interface for the components' reactive interface, enabling clearer contracts between the compositional logic and the consuming components.

As the ecosystem matures, Vue developers are presented with a myriad of choices in component architecture. With the Composition API, the pathway towards heightened abstraction and reusability of logic opens up. It's a path that necessitates a keen eye for balancing the overhead of abstraction against the clarity and simplicity it can bring to an application's architecture. As such, the Composition API does not merely offer a new set of features; it presents a philosophical shift towards more organized, intentional, and scalable Vue applications.

Stateless vs. Stateful Component Architecture

In the Vue.js ecosystem, the distinction between stateless and stateful components is crucial for managing complexity and ensuring a clear contract of responsibility within an application. Stateless components, often called presentation or dumb components, are primarily concerned with how things look; they accept data through props and emit events up to their parent elements, allowing them to be highly reusable and testable. On the other hand, stateful components, also known as smart or container components, are responsible for how things work; they maintain a state and usually serve as data sources for their child components.

Consider a stateless UserProfile component, designed to receive a user object via props and display the user's information. It does not need to know where the data comes from or how to fetch it, encapsulating the UI logic for rendering that particular piece of data.

export default {
  name: 'UserProfile',
  props: {
    user: Object

  <div class="user-profile">
    <h1>{{ }}</h1>
    <p>Email: {{ }}</p>

In contrast, a UserContainer component maintains the state of the user data by fetching it from an API and passes it down to the UserProfile. This component encapsulates the data-fetching logic, reacting to lifecycle events, and managing the state.

import UserProfile from './UserProfile.vue';
import axios from 'axios';

export default {
  name: 'UserContainer',
  components: {
  data() {
    return {
      user: null
  created() {
  methods: {
    async fetchUser() {
      try {
        const response = await axios.get('/api/user');
        this.user =;
      } catch (error) {

  <div class="user-container">
    <UserProfile v-if="user" :user="user" />

Choosing between stateless and stateful components often hinges on the principle of separation of concerns. By encapsulating the UI rendering in stateless components and the business logic in stateful ones, developers can streamline the complexity of updates and maintenance. For example, updating the UI layout of user profiles would require changes to the UserProfile component, while modifications to data fetching would occur in the UserContainer.

However, while stateful components offer the advantage of being data-aware, they also introduce a higher level of coupling to the application state, which can make them less reusable and more challenging to test. Large-scale applications might benefit from isolating the state management using global state managers like Vuex to bridge the gap between reusability and statefulness.

A common mistake within Vue.js component design pertains to over-populating stateful components with both data and UI responsibilities, leading to bloated and less maintainable code. To correct this, developers should strive to minimize the responsibilities of stateful components, focusing them on data management and delegating UI rendering to stateless child components. This approach enhances the scalability of the application while retaining a clean and organized component structure, accommodating for complex application requirements and facilitating easier debugging and testing.

As state management strategies evolve, and applications grow in complexity, thoughtful considerations are necessary: Which components truly need to be stateful? Can smart components be further decomposed to enhance modularity and testability? And how can stateless components be optimized to ensure maximum reusability across different parts of your application? Answers to these questions help refine architecture, leading to sophisticated and well-structured Vue.js applications.

Handling Cross-Component Communication and State

In Vue.js 3, managing state across components demands a nuanced approach, especially when dealing with complex hierarchies. The introduction of the provide and inject pattern allows for a more strategic and less prop-heavy state management by enabling ancestor components to propagate dependencies directly to descendants. This significantly streamlines the process in deeply nested structures but should be used judiciously. Overuse can introduce an opaque data flow that obscures the source of state changes, making reactivity harder to follow and debug.

// Ancestor component providing 'theme' state
setup() {
  const theme = ref('dark');
  provide('theme', theme);

// Descendant component injecting 'theme' state
setup() {
  const theme = inject('theme');
  return { theme };

When it comes to handling reactive data, Vue 3's Composition API presents ref as a robust solution for creating mutable, reactive references which can be passed around components facilitating both communication and state sharing. A common pitfall, however, is not recognizing that for objects and arrays, one should use the reactive() function to maintain optimal reactivity and manage state effectively within the component's context.

// Using 'ref' for primitive values
const counter = ref(0);

// Using 'reactive' for complex state
const state = reactive({ count: 0, name: 'Vue' });

While Vuex has long been the go-to for state management in Vue, it tends to add unnecessary complexity to more straightforward applications. It's robust for enterprise-level applications but can overwhelm smaller projects where components simply need to synchronize or orchestrate state changes. The Vue 3 Composition API mitigates this by facilitating state management with less overhead, enabling developers to construct a global state that seamlessly integrates with local component state while retaining more control over reactivity and encapsulation.

Developers should be cautious not to default to a global state when component-level state would suffice. Encapsulating logic within composables ensures a clean separation of concerns and enhances reusability. This modular approach, aided by Vue 3's explicit reactive system, paves the way for a clean codebase with clearly defined responsibilities.

// Creating a composable to encapsulate and share logic
function useCounter() {
  const count = ref(0);
  function increment() {
  return { count, increment };

In making decisions about state management, ponder the balance between local and global state. How might lifting state up to a global context impact the reusability and clarity of components in your Vue.js 3 application architecture? The flexibility in Vue.js 3's toolset is abundant – the challenge lies in employing these mechanisms to craft a scalable and maintainable application without compromising on performance or introducing unnecessary complexity.

Performance Optimization and Best Practices

Leveraging lazy loading in Vue.js 3 can significantly enhance the performance of applications, particularly those that carry a substantial number of components or deal with hefty modules. Code splitting, a related technique, can be achieved through dynamic imports where components are imported only when needed. This strategy not only reduces the initial load time by downloading chunks of code on-demand but also mitigates the potential impact on memory usage. For instance, integrating Vue's defineAsyncComponent can delineate boundaries within the app where code splitting can occur, providing a seamless user experience without lags in interaction.

const AsyncComponent = defineAsyncComponent(() =>

In regard to caching strategies, developers can capitalize on Vue 3’s reactivity system which smartly caches computed properties. However, improper use of this system can lead to unintended side effects and performance hits. Therefore, understanding when to use caching and when to compute on the fly is vital. For example, avoid the temptation of overusing computed properties for data that doesn't change often, as it adds unnecessary layers of dependency tracking. Instead, favor methods for non-reactive complex calculations where caching is not beneficial.

const sortedList = computed(() => {
  // Create a copy before sorting to prevent mutating the reactive source
  return myReactiveList.slice().sort((a, b) => a.value - b.value);

To enforce a robust structure while building scalable Vue.js 3 applications, following best practices is paramount. Emphasize modularity by breaking down complex components into smaller, focused units, which can substantially ease the testing and maintenance process. Embrace the Composition API for its superior reusability of logic across components, and cautiously apply the provide and inject functions to prevent obscure state relations. Ensure to provide thorough validation and prop typing to strengthen component contracts, thereby preventing costly errors at runtime.

In addition to structuring, prioritize performance budgeting to keep a check on the application size and load times. Employ performance profiling tools to detect bottlenecks and use techniques like debouncing or throttling for event handlers that might invoke resource-intensive methods. Keeping template expressions simple and offloading complex logic to computed properties or methods also helps maintain a healthy performance profile.

  <div>{{ computedFullName }}</div>

export default {
  props: {
    firstName: StringConstructor,
    lastName: StringConstructor
  computed: {
    computedFullName() {
      return `${this.firstName} ${this.lastName}`;

Finally, consider the sensitive balance of reactivity and performance in large-scale applications. While Vue's reactivity system is powerful, overuse can escalate the overhead and impact performance. Be tactful about introducing reactive properties, particularly for data that experiences infrequent changes. The aim should be to achieve reactive granularity without undermining the application’s responsiveness or user experience. Reflect on these optimizations to write high-performing, scalable Vue.js 3 applications.


In this article, we explore the new component architecture in Vue.js 3, specifically focusing on the Composition API and the shift from the Options API. We discuss the benefits of the Composition API for code organization and reuse, as well as the importance of balancing stateful and stateless components in application design. We also delve into cross-component communication and state management strategies, emphasizing the use of provide/inject for prop-heavy scenarios. Additionally, we touch on performance optimization techniques such as lazy loading, code splitting, caching, and best practices for modularity and performance budgeting. The key takeaway is that Vue.js 3 offers developers powerful tools and techniques to build scalable and maintainable applications. As a challenge, readers are encouraged to refactor their existing Vue.js 2 applications to leverage the Composition API and explore the benefits of the new component architecture.

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