How do you handle loading skeletons or placeholders when using dynamic imports in JavaScript?

13 Oct 2023

In modern web development, dynamic imports have become a popular technique for improving performance by loading JavaScript modules on-demand. However, when dynamically importing modules, it’s crucial to provide a good user experience by displaying loading skeletons or placeholders until the asynchronous import is complete.

Loading skeletons or placeholders effectively communicate to users that content is being loaded and helps to reduce perceived load times. In this article, we’ll explore different approaches to handle loading skeletons or placeholders when using dynamic imports in JavaScript.

Option 1: Pre-defined Loading Skeletons

One approach is to pre-define loading skeletons for different components or modules. These loading skeletons can be simple HTML or CSS structures that visually resemble the final component but don’t contain the actual dynamic content.

When dynamically importing a module, you can replace the loading skeleton with the actual content once the import is complete. This can be achieved using JavaScript by manipulating the DOM.

Here’s an example of how this can be implemented:

import('./myModule.js')
  .then((module) => {
    const content = module.default;
    const container = document.getElementById('container');
    container.innerHTML = content;
  })
  .catch((error) => {
    console.error('Error loading module:', error);
  });

In this example, the myModule.js module is imported dynamically. Once the import is successful, the container element’s inner HTML is replaced with the content from the module.

Option 2: Conditional Rendering

Another approach is to conditionally render loading skeletons or placeholders based on the module’s loading state. This can be achieved by leveraging JavaScript’s import() function and a state management library like React.

Here’s an example using React:

import React, { useState, useEffect } from 'react';

function MyComponent() {
  const [isLoading, setIsLoading] = useState(true);
  const [content, setContent] = useState(null);

  useEffect(() => {
    import('./myModule.js')
      .then((module) => {
        const loadedContent = module.default;
        setContent(loadedContent);
      })
      .catch((error) => {
        console.error('Error loading module:', error);
      })
      .finally(() => {
        setIsLoading(false);
      });
  }, []);

  return (
    <div>
      {isLoading ? <LoadingSkeleton /> : content}
    </div>
  );
}

In this example, the MyComponent renders a loading skeleton when isLoading is true, and the actual content once the module is loaded. The use of useState and useEffect hooks helps manage the component’s loading state and dynamically import the module.

Conclusion

When using dynamic imports in JavaScript, it is important to consider the user experience during the loading process. By implementing loading skeletons or placeholders, you can provide visual feedback to users while the modules are being loaded asynchronously.

Whether you choose pre-defined loading skeletons or conditional rendering, the goal is to ensure a smooth loading experience for your users. Experiment with these techniques and find the approach that best fits your application’s needs.

References

Dynamic Import
Using dynamic imports in JavaScript #javascript #dynamicimports