How to improve Website Performance by Lazy loading technique ?

SEO Help and Tips

How to improve Website Performance by Lazy loading technique ?

Lazy loading is a technique that helps improve website performance by loading resources only when they are needed, rather than loading everything upfront during the initial page load. This can significantly reduce the initial loading time, especially for larger websites or applications.

When you have certain JavaScript code or modules that are not needed immediately when the page loads, you can defer their loading until they are required. This can be beneficial for parts of your website that are hidden by default or appear based on user interactions, such as pop-up modals, tabs, or sections loaded via AJAX.

Here's how you can implement lazy loading for JavaScript:

Dynamic Imports (ES modules): If you're using ECMAScript modules (ES modules), you can use dynamic imports to load modules lazily. With dynamic imports, you can conditionally load modules when needed.

  <script type='text/javascript'>

// Instead of importing the module at the top level

// import { someFunction } from './my-module.js';

// Use dynamic import when needed

const button = document.getElementById('lazyLoadButton');

button.addEventListener('click', async () => {

  const { someFunction } = await import('./my-module.js');

  someFunction();

});

</script>

Intersection Observer API: If you want to lazy load JavaScript based on an element's visibility in the viewport, you can use the Intersection Observer API. This allows you to observe when an element becomes visible, and then you can load the required JavaScript code.

  <script type='text/javascript'>

const lazyLoadScript = document.createElement('script');

lazyLoadScript.src = 'path/to/lazy-load-script.js';

const lazyLoadObserver = new IntersectionObserver((entries, observer) => {

  entries.forEach(entry => {

    if (entry.isIntersecting) {

      document.body.appendChild(lazyLoadScript);

      observer.unobserve(entry.target);

    }

  });

});

// Element to observe for visibility

const lazyLoadTrigger = document.getElementById('lazyLoadTrigger');

lazyLoadObserver.observe(lazyLoadTrigger);

</script>

Third-Party Libraries: Some third-party libraries and tools provide lazy loading capabilities. For example, if you're using React, there are libraries like React.lazy() and Suspense that allow lazy loading of components.

Remember that while lazy loading can greatly benefit performance, it's essential to use it judiciously. Carefully consider which parts of your website can benefit from lazy loading, and test thoroughly to ensure that the lazy-loaded components or scripts work as expected. Lazy loading should be used to enhance the user experience by reducing initial load times, not at the expense of functionality or usability.

Some customization on this code before use

before using the code for lazy loading, there are a few customizations and considerations you should make based on your specific use case and project requirements:

Element to Observe: In the Intersection Observer example, you'll need to specify the element that you want to observe for visibility. Update the lazyLoadTrigger variable to target the appropriate element in your HTML that will trigger the lazy loading.

const lazyLoadTrigger = document.getElementById('yourLazyLoadElementId');

Lazy Loaded Script: Update the src attribute of the lazyLoadScript variable to point to the JavaScript file you want to load lazily.

lazyLoadScript.src = 'path/to/your/lazy-load-script.js';

Fallback for No JavaScript Support: Consider providing a fallback for users who have JavaScript disabled in their browsers. You can place the <script> tag for the lazily loaded script directly in the HTML as a fallback option.

Error Handling: Add error handling to handle cases where the lazy-loaded script fails to load or execute correctly.

Polyfills: If you are using Intersection Observer and other modern JavaScript features, consider adding appropriate polyfills for older browsers that do not support them.

lazyLoadScript.addEventListener('error', () => {

  console.error('Error loading lazy-loaded script.');

});

Bundle Splitting: In more complex projects, you might have different entry points and multiple lazy-loaded scripts. You can set up Webpack or another bundler to handle code splitting and automatically generate separate bundles for different parts of your application.

Testing: Thoroughly test the lazy-loaded components and scripts to ensure they work as intended. Test scenarios where the lazy-loading element becomes visible, as well as scenarios where it does not (e.g., if it's hidden by default).

Performance Considerations: While lazy loading improves initial page load, it may introduce a slight delay when the lazy-loaded content is requested for the first time. Evaluate whether the benefits of lazy loading outweigh this potential delay for your specific use case.

Remember that the code provided earlier is a basic example to demonstrate the concept of lazy loading. The actual implementation may vary depending on your project's complexity and the libraries or frameworks you are using. Always test thoroughly to ensure the lazy loading works correctly and enhances the user experience.