NashTech Insights

Code Splitting and Lazy Loading with Modules in JavaScript

Alka Vats
Alka Vats
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Code splitting and lazy loading are techniques used in JavaScript applications to improve performance by optimizing the loading and execution of code. These techniques enable developers to split their application code into smaller, manageable chunks and load them on demand when needed.

In this blog, we will explore code splitting and lazy loading with modules, understand their benefits, and implementation strategies, & provide practical examples.

If you want to learn about the comparison between typescript and javascript, you can refer here.

Code Splitting:

Code splitting is dividing your application code into smaller chunks, typically based on different routes, components, or features. By splitting the code, you can load only the required portions of your application when needed, reducing the initial load time and improving performance.

Let’s consider an example using a popular bundler like Webpack:

// App.js
import("./components/Home").then((module) => {
  const HomeComponent = module.default;
  // Render the HomeComponent

import("./components/About").then((module) => {
  const AboutComponent = module.default;
  // Render the AboutComponent

Therefore, In this example, instead of directly importing the components, we use dynamic imports with the import() function. The import() function returns a promise that resolves to the module containing the requested component. With code splitting, only the necessary component code will be loaded when a user navigates to the corresponding route, reducing the initial bundle size.

Lazy Loading:

Lazy loading is closely related to code splitting and involves loading code or resources only when they are required, typically triggered by a specific user action or a specific point in the application flow. This technique helps optimize the loading time of large applications, allowing them to load faster and improving the user experience.

Consider the following example:

// Button.js
const Button = () => {
  const handleClick = () => {
    import("./analytics").then((module) => {
      module.trackEvent("Button Click");

  return <button onClick={handleClick}>Click me</button>;

Therefore, In this example, when the handleClick the function is invoked, the import() function is called to load the analytics module, which contains tracking functionality. By lazy loading the analytics module, you avoid loading it unnecessarily during the initial page load. The module is loaded and executed only when the user interacts with the button.

Benefits of Code Splitting and Lazy Loading:

a. Faster Initial Load:

By splitting code into smaller chunks and loading only the required portions, the initial load time of the application is reduced, enhancing the user experience.

b. Improved Performance:

Loading only the necessary code and resources as needed reduces the amount of data transferred and speeds up the application’s performance.

c. Better Resource Management:

Code splitting and lazy loading allow you to optimize the usage of system resources by deferring the loading of non-essential components until they are required.

Tooling and Frameworks:

Modern JavaScript bundlers like Webpack, Rollup, and Parcel provide built-in support for code splitting and lazy loading. Thus, Popular frameworks such as React, Angular, and Vue.js also offer mechanisms for implementing code splitting and lazy loading in their respective ecosystems.

Considerations and Best Practices:

a. Identify Code Splitting Opportunities:

Analyze your application’s structure and identify components or features that can be split into separate modules.

b. Set Chunk Sizes:

Configure your bundler to generate optimized chunks based on your application’s requirements, striking a balance between smaller bundle sizes and reducing the number of network requests.

c. Code Splitting Strategies:

Consider different code-splitting strategies like route-based splitting, component-based splitting, or dynamic imports to suit your application’s needs.

d. Loading Indicators:

Implement loading indicators or placeholders to provide visual feedback to users while the required code or resources are being loaded.


Code splitting and lazy loading are powerful techniques that help optimize JavaScript applications. It improves performance, reduces initial load times, and enhances the user experience. By splitting code into smaller chunks and loading only what is necessary, you can achieve faster load times and better resource management. In this comprehensive guide, we explored code splitting and lazy loading with modules, providing practical examples and discussing their benefits. Embrace these techniques in your JavaScript

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Alka Vats

Alka Vats

Alka Vats is a Software Consultant at Nashtech. She is passionate about web development. She is recognized as a good team player, a dedicated and responsible professional, and a technology enthusiast. She is a quick learner & curious to learn new technologies. Her hobbies include reading books, watching movies, and traveling.

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