Smart Resource Loading: Load What You Need, When You Need It

Jun 19, 2025 - 2 min read

Conditional Resource Loading: The Smart Way to Optimize Performance

Modern websites often require numerous resources—JavaScript libraries, CSS frameworks, fonts, and more—to deliver rich experiences. However, loading everything upfront can significantly impact performance, especially on slower connections or less powerful devices.

The Smart Approach: Load Resources Conditionally

With Boostify’s content injection capabilities, you can implement sophisticated conditional loading strategies:

(async () => {
    try {
        // Example 1: Load based on user interaction
        document.getElementById('open-chat').addEventListener('click', async () => {
            await bstf.loadScript({
                url: 'https://cdn.example.com/chat-widget.js',
                appendTo: 'body',
            });
        });

        // Example 2: Load based on viewport/element visibility
        const observer = new IntersectionObserver(async (entries) => {
            if (entries[0].isIntersecting) {
                await bstf.loadStyle({
                    url: 'https://cdn.example.com/advanced-animations.css',
                    appendTo: 'head',
                });
                observer.disconnect(); // Load only once
            }
        });
        observer.observe(document.querySelector('.animation-container'));

        // Example 3: Load based on device capabilities
        if (window.matchMedia('(min-width: 768px)').matches) {
            // Load desktop-specific enhancements
            await bstf.loadScript({
                url: '/assets/js/desktop-features.js',
                appendTo: 'body',
            });
        } else {
            // Load mobile optimizations
            await bstf.loadScript({
                url: '/assets/js/mobile-optimizations.js',
                appendTo: 'body',
            });
        }

        // Example 4: Load based on user preferences
        if (localStorage.getItem('prefers-advanced-features') === 'true') {
            await bstf.loadScript({
                url: '/assets/js/advanced-features.js',
                appendTo: 'body',
            });
        }

    } catch (error) {
        console.error(error);
    }
})();

The Benefits Are Clear

Optimized Performance: Load only what users actually need based on their context.
Better User Experience: Prioritize critical resources first, then enhance progressively.
Reduced Data Usage: Save bandwidth by avoiding unnecessary resource downloads.
Device-Appropriate Experiences: Deliver the right experience for each device type.

Real-World Use Cases

Chat Widgets: Load chat functionality only when a user clicks the chat icon
Media-Rich Content: Load high-resolution images or videos only on capable devices
Advanced Interactions: Add sophisticated UI behaviors only when users scroll to that section
Feature Toggles: Enable experimental features only for users who opt in

Implementation Strategies

1. User Interaction-Based Loading

Load resources in response to specific user actions:

element.addEventListener('click', async () => {
    await bstf.loadScript({ url: 'resource.js' });
    // Initialize newly loaded functionality
});

2. Visibility-Based Loading

Load resources when elements come into view:

const observer = new IntersectionObserver(async (entries) => {
    if (entries[0].isIntersecting) {
        await bstf.loadStyle({ url: 'animations.css' });
    }
});
observer.observe(element);

3. Capability-Based Loading

Adapt loading based on device capabilities:

if ('IntersectionObserver' in window && 'requestIdleCallback' in window) {
    // Load advanced features for modern browsers
} else {
    // Load fallback for older browsers
}

4. Preference-Based Loading

Respect user preferences for resource loading:

if (localStorage.getItem('data-saver') === 'true') {
    // Load lightweight alternatives
} else {
    // Load standard resources
}

By implementing conditional resource loading strategies, you can create websites that are both feature-rich and highly performant, adapting to each user’s unique context and needs.