How to implement lazy loading in OutSystems to defer non-critical content loading?

Implementing Lazy Loading in OutSystems to Defer Non-Critical Content Loading

Lazy loading is an essential performance optimization strategy that delays the loading of non-critical content in your application until it is actually needed, reducing initial load time and improving responsiveness. Here’s a comprehensive guide to implementing lazy loading in OutSystems.

Prerequisites

• An OutSystems account with required permissions for creating and modifying applications.
• Familiarity with Service Studio, especially screen and widget management.
• Basic understanding of web concepts such as asynchronous loading and deferred content.

Understanding Lazy Loading

• Lazy loading defers the loading of resources until they’re needed, improving page load time initially.
• It is beneficial for optimizing resources like images, data lists, and other content-heavy elements on pages.

Steps to Implement Lazy Loading in OutSystems

1. Identifying Non-Critical Content

• Review your OutSystems screen and determine which elements do not require immediate loading (e.g., images that are not in the initial viewport, large lists).

2. Use Placeholders for Deferred Content

• Create placeholder elements to indicate where content will appear after loading, providing a seamless user experience.
• Utilize OutSystems widgets like “Containers” or “Images” to create placeholders.

3. Implementing Lazy Loading for Images

• Select the Image widget you want to apply lazy loading to.
• In the image properties, set the "Image loading" option to "Lazy". This ensures that the image is only loaded when it enters the viewport.
• Ensure that appropriate fallback content or styling is provided for the image's placeholders.

4. Lazy Loading Lists or Data Grids

• Use OutSystems' built-in data pagination controls to load data incrementally.
• Set a reasonable initial load size, and configure "On Scroll" or other triggers to load additional data as the user interacts with the page.
• Create logic in the associated aggregate or SQL query to fetch data based on user interaction or position.

5. Conditionally Loading Widgets

• Use OutSystems "If" widgets to determine when certain elements should be loaded/rendered.
• Link the widget visibility or rendering condition to a user action or scroll position logic.
• Run any additional scripts or initialization functions only when the widget becomes visible.

6. Enhancing with JavaScript for Advanced Lazy Loading

• If native OutSystems controls aren’t enough, you can enhance lazy loading with JavaScript for better control.
• Write JavaScript that listens for scroll events and dynamically loads components upon nearing the viewport.

Testing and Optimizing Lazy Loading

• After implementation, use tools like Chrome DevTools to analyze network requests and verify deferred loading behavior.
• Ensure that user interactions like scrolling and clicking load the expected resources effectively.
• Test across different devices and browsers to ensure that lazy loading behaves consistently.
• Monitor performance improvements by measuring time-to-interactive and page loading times before and after lazy loading.

Deploying the Application

• After thorough testing, deploy your application to a staging environment to ensure all lazy-loaded elements work as expected.
• Gather feedback from users on performance improvements and make iterative enhancements based on practical use.
• Finalize deployment to the production environment applying any necessary configurations for scaling the solution.

By following these steps, you can effectively implement lazy loading in OutSystems, enhancing your application's performance by deferring non-critical content loading, improving user experience especially on resource-intensive screens.