The core idea of a responsive system

Vue 3's reactivity system, based on Proxy, offers significant improvements over Vue 2's Object.defineProperty. By intercepting object operations with Proxy, dependencies are collected in getters and updates are triggered in setters. Each reactive property is associated with a dependency set—when the property is accessed, the currently running side effect is recorded into the dependency set. When data changes, the system looks up the corresponding dependency set and executes all side effect functions. Vue 3 uses the `effect` function to create and manage side effects, providing multiple ways to create reactive data, such as `ref` and `reactive`. Shallow reactive objects only handle top-level properties. The system includes various performance optimizations, such as bitwise operations to mark dependency relationships and microtask queues for batched updates. When reactive data changes, it triggers component re-rendering, involving virtual DOM diffing and updates. Edge cases like circular references, primitive value conversion, etc., are also handled. In development mode, detailed debugging information is provided. The system is entirely written in TypeScript, offering robust type support.

The monorepo code organization approach

Monorepo is a code organization approach where multiple projects or modules are stored in a single repository. The Vue 3 source code adopts this structure, centralizing the management of core libraries, compilers, runtimes, and other modules through a workspace mechanism to facilitate dependencies and collaboration between modules. Monorepo offers advantages such as easier code sharing, simpler dependency management, and unified builds and testing. The typical structure of Vue 3's monorepo includes functional modules under the `packages` directory, such as `compiler-core`, runtime, and `reactivity`. Dependencies between modules are declared using the workspace protocol to ensure the use of the latest local code during development. The workflow supports cross-package modifications and unified version releases. The build system is designed to support parallel builds and incremental compilation. For debugging, tools like `pnpm link` or VS Code compound launch configurations can be used. The testing strategy employs Jest for cross-package testing, and code standards are unified through shared ESLint configurations. Performance optimization techniques include build caching and task parallelization. Compared to Multirepo, Monorepo excels in code sharing and dependency management. Typical solutions to challenges include detecting circular dependencies and resolving version conflicts. After transitioning from Vue 2's Multirepo to Monorepo, Vue 3 achieved synchronized modifications between the compiler and runtime, as well as full CI testing in a single run. As the scale grows, functional partitioning and automation tools maintain maintainability. External projects can depend on Vue 3's local development version via the workspace protocol, facilitating debugging and feature development.

Overview of Vue 3's Overall Architecture

Vue 3's architecture revolves around a reactive system, compiler, and runtime core, adopting a monorepo management approach. The reactive system replaces `Object.defineProperty` with `Proxy`, addressing Vue 2's limitations. Compiler optimizations include static node hoisting and patch flags, while runtime core improvements enhance the virtual DOM and component system. The Composition API resolves complex component code organization issues. The modular architecture supports on-demand usage and custom renderers. Performance optimizations cover compile-time, virtual DOM, and memory management. A robust type system provides comprehensive support, and the custom renderer API extends applications to non-DOM environments. These enhancements significantly improve Vue 3's performance and development experience.

Performance monitoring tools

Performance monitoring tools for Vue.js applications are crucial for addressing rendering bottlenecks, memory leaks, and inefficient code in complex applications. The browser's developer tools Performance panel can record runtime data such as script execution time and memory usage. Vue DevTools provides component-level performance analysis, including rendering time waterfall charts and custom markers. Webpack analysis tools help optimize build size. Production environment APM solutions like Sentry can monitor page load and route navigation performance. Custom instrumentation systems can track the duration of critical operations. Memory leak detection tools identify uncleared events and timers. Rendering optimization techniques include `v-once` and virtual scrolling. Benchmarking solutions enable continuous performance regression testing. These tools and methods collectively ensure the high-performance operation of Vue applications.

Preloading and prefetching strategies

Preloading and prefetching are key techniques for optimizing web performance. Preloading forces the browser to immediately load critical resources, while prefetching loads potentially needed resources during idle time. In Vue.js, `webpackPreload` enables component preloading for critical resources used in the current route, whereas `webpackPrefetch` prefetches resources likely needed in future navigations. These generate `<link rel="preload">` and `<link rel="prefetch">` tags in HTML, respectively. A mixed strategy is practical in real-world applications—for example, an e-commerce site might preload main components while prefetching related ones. Performance tests show hybrid strategies deliver the best results. Note that excessive preloading can block rendering, and prefetching should be used cautiously on mobile. Dynamic routes require special handling, and server-side rendering frameworks like Nuxt.js have dedicated configurations. Lighthouse tests demonstrate that hybrid strategies significantly improve metrics. Additionally, strategies can be dynamically adjusted based on network conditions, and Service Workers can manage caches for finer control.

Bundle size optimization

Optimizing the build size of a Vue.js project is crucial for enhancing user experience, especially on mobile devices and in poor network conditions. Using webpack-bundle-analyzer to analyze module distribution is the starting point for optimization. Code splitting strategies, including route-based lazy loading and component-level splitting, effectively reduce the initial load size. Third-party library optimization involves on-demand imports and lightweight alternatives, while tree shaking ensures the removal of unused code. Image resource optimization includes compression and the use of modern formats. Build configuration optimizations, such as removing source maps and reasonable chunk splitting, further improve performance. Runtime optimizations cover gzip compression and preload/prefetch. Long-term maintenance requires regular bundle analysis and dynamic polyfilling. Advanced techniques involve WebAssembly and server-side rendering. Finally, establishing a performance monitoring mechanism to continuously track build size changes ensures the project remains efficient over time.

Animation performance optimization

The key to animation performance optimization lies in reducing browser repaints and reflows. In Vue.js, animation performance issues typically arise from frequent DOM operations, complex CSS properties, and improper animation triggering timing. Optimization directions mainly include using transform and opacity properties, reducing layout thrashing, properly utilizing will-change, avoiding forced synchronous layouts, etc. CSS hardware acceleration can be achieved by replacing top/left with transform. Reducing unnecessary reactive data can improve performance. Using requestAnimationFrame instead of setTimeout/setInterval is recommended. For list animation optimization, FLIP technique or disabling animations for certain elements can be applied. When destroying components, attention should be paid to animation handling to prevent memory leaks. For scroll animations, direct DOM modifications should be avoided. SVG animations should prioritize CSS transforms. Integrating performance monitoring tools can help identify performance issues. Animations need to be coordinated with Vue's lifecycle. Dynamic component transitions should use mode="out-in" for optimization.

Long list rendering solution

Long list rendering is a common performance bottleneck in front-end development. Traditional rendering methods can cause page lag, high memory usage, and even browser crashes. Virtual scrolling solves this problem by only rendering elements within the visible area. Its core idea is to calculate the height of the visible region, determine the range of currently visible elements based on the scroll position, and render only those visible elements while using placeholder elements to maintain the total height of the list. In the Vue ecosystem, there are mature virtual scrolling solutions like `vue-virtual-scroller`, or you can implement a custom virtual scrolling component. Pagination and infinite scrolling are another solution, which can be combined with virtual scrolling for better performance. Performance optimization techniques include using `Object.freeze` to avoid unnecessary re-rendering and leveraging Web Workers to handle large datasets. These methods effectively improve long list rendering performance and enhance user experience.

Memory management recommendations

In a Vue.js application, memory management is crucial for performance. Properly controlling component lifecycles, avoiding memory leaks, and optimizing data storage can enhance smoothness. When components are destroyed, it's essential to clean up event listeners, timers, and third-party library instances. For large datasets, virtual scrolling and paginated loading should be adopted. Reactive data should be used judiciously, avoiding full-object reactivity. Third-party libraries like chart libraries require attention to destroying image resources, which can be optimized via lazy loading. The Vuex state tree should be modularized. Closures may cause memory leaks and must be handled carefully. Dynamic components combined with keep-alive should control cache size. CPU-intensive tasks can be offloaded to Web Workers to reduce main thread pressure.

Code splitting and Tree-shaking

Code splitting is a technique that breaks code into smaller chunks for on-demand loading. In Vue.js, this is achieved through dynamic imports. Webpack's SplitChunks configuration allows fine-grained control over splitting strategies. Tree-shaking eliminates unused code through static analysis. On-demand loading for Vue component libraries requires Babel plugins, while dynamic imports combined with magic comments enable preloading and prefetching. Performance monitoring utilizes webpack-bundle-analyzer to analyze output. SSR requires special handling for async components. Webpack 5's Module Federation supports micro-frontend architectures. Common issues include duplicate dependencies, CSS splitting, and load failure handling. Optimizing bundling results through proper configuration enhances application performance.