Angular is a popular framework for building dynamic web applications, known for creating powerful and interactive user experiences. However, as projects grow, performance issues can arise, making optimisation essential to maintain smooth functionality and guarantee the finest user experience. What are the best practices to improve the performance of Angular applications?
Lazy loading of modules
Lazy loading is a technique that loads only the modules required at a given moment, reducing the initial load time and ensuring unused resources do not overwhelm the user’s browser. Tools like Angular CLI, which streamline the quick and easy generation of Angular projects, support the automatic creation of modules with lazy loading, simplifying the implementation of this technique.
OnPush Change Detection
By default, Angular uses a reference-based change detection strategy that triggers checks on all components whenever the application’s state changes. Switching to the OnPush strategy optimizes this process by limiting checks to only when a component’s inputs (@Input properties) are modified. This reduces unnecessary change detection cycles, making it particularly beneficial in large applications where performance gains can be substantial.
Unsubscribing from Observable
Improper handling of Observable subscriptions can lead to memory leaks. Always unsubscribe when necessary, using techniques like the takeUntil operator. Alternatively, using AsyncPipe in templates automatically manages subscriptions and cancels them when the component is destroyed.
Reducing bundle size
An excessively large bundle negatively affects load time. Fortunately, this can be mitigated with the right approach:
- Utilise tree-shaking to remove unused code. While Angular CLI supports tree-shaking, it’s also worth manually reviewing dependencies to avoid unnecessary libraries.
- Use @angular/material or other Angular libraries modularly by importing only the components that are required.
Server-side rendering (SSR) with Angular Universal
Angular Universal enables server-side rendering (SSR), which can significantly boost both load times and SEO. With SSR, content is displayed faster, reducing the load on the user’s browser and enhancing the user experience — especially on less powerful devices.
Asynchronous resource loading
Asynchronously loading resources, such as scripts or external libraries, speeds up page rendering. Additionally, using async or defer attributes in scripts can prevent blocking the rendering of the page.
Minimising components and Change Detection
Deep component hierarchies and redundant Change Detection operations can burden applications. Avoiding overly deep component structures and using techniques like memoization of results can be effective in performance optimisation.
Optimised production builds with Angular CLI
Angular CLI provides built-in optimisation mechanisms for production builds. Running the ng build –prod command automatically applies minification (reducing the source code by removing unnecessary characters without affecting functionality), tree-shaking, and other optimisations. Ensuring your builds are configured properly will maximise performance and reduce unnecessary overhead.
Optimised resource management
Large static resources, such as images and fonts, can prolong application load times. To tackle this, use Webpack Bundle Analyzer to analyse your application’s bundle and identify large resources that can be optimised or split into smaller parts. Additionally use formats like WebP for images and reduce the size of other static assets for faster load times.
Performance monitoring and analysis
Consistently monitoring your application can help identify bottlenecks and areas that need improvement. Tools like Angular DevTools, Chrome DevTools, and Lighthouse offer advanced profiling features, while platforms like Sentry and New Relic provide performance monitoring in production environments.
Reducing external HTTP requests
Too many HTTP requests to the server can slow down an application. To avoid this, consider techniques such as:
- Aggregating HTTP requests using techniques like debouncing, caching, or batching.
- Using mechanisms like HttpInterceptor to optimise HTTP requests management.
Limiting external libraries
Each additional library introduces extra code to the application, inflating the bundle size. Only choose libraries that are essential and try to implement other functionalities using Angular’s native capabilities.
Summary
Optimising an Angular application is an ongoing process that requires constant monitoring and adaptation. By focusing on reducing unnecessary computations, minimising renderings, and optimising resource management, you can achieve smoother, faster, and more efficient applications. Following these practices will ensure your Angular applications deliver an outstanding user experience.
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