JavaScript Dynamic Import: A Beginner’s Guide with Examples

Bharath Kumar Murugan
3 min readApr 15, 2023

If you’re a JavaScript developer, you’re probably familiar with the import statement that is used to load modules. However, in addition to the traditional import statement, JavaScript also provides a dynamic import() function that allows you to load modules dynamically at runtime.

Dynamic import is a relatively new feature that was introduced in ECMAScript 2018. It allows you to load modules on-demand, which can help to improve the performance of your application by reducing the initial load time.

In this article, we’ll discuss how dynamic import works, why it’s useful, and how you can use it in your projects.

How Dynamic Import Works

In traditional JavaScript, modules are loaded synchronously when the script is parsed. This means that all modules are loaded before the script is executed, even if they are not immediately needed.

Dynamic import allows you to load modules asynchronously, which means that they are loaded on-demand when they are actually needed. This can help to improve the performance of your application, as it reduces the initial load time and improves the overall responsiveness of your app.

The syntax for dynamic import is as follows:

import(moduleSpecifier)
.then((module) => {
// Use module here
})
.catch((error) => {
// Handle error here
});

The import() function returns a promise that resolves with the module object when the module has been loaded. You can then use the module object to access the exports of the module.

Let’s take a look at an example to see how this works in practice.

Example

Suppose we have a module called math.js that contains a function called add that adds two numbers:

// math.js
export function add(a, b) {
return a + b;
}

We can use dynamic import to load this module asynchronously as follows:

// main.js
import("./math.js")
.then((module) => {
const result = module.add(2, 3);
console.log(result); // Output: 5
})
.catch((error) => {
console.error(error);
});

In this example, we use dynamic import to load the math.js module asynchronously. When the module has been loaded, we use the module object to call the add function and print the result to the console.

Benefits of Dynamic Import

Dynamic import has several benefits that make it a useful tool for JavaScript developers:

  1. Improved performance: By loading modules on-demand, dynamic import can help to improve the initial load time of your application and improve the overall performance.
  2. Better resource management: Dynamic import allows you to manage your application resources more efficiently by loading modules only when they are needed.
  3. Smaller bundle sizes: By loading modules on-demand, you can reduce the size of your application bundle, which can help to improve the loading time of your app.

Conclusion

Dynamic import is a powerful feature in JavaScript that allows you to load modules asynchronously and improve the performance of your application. While it may not be necessary for all projects, it can be a useful tool for managing resources and reducing bundle sizes. By understanding how dynamic import works and how to use it, you can take advantage of this feature in your own projects and improve the overall user experience.

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Bharath Kumar Murugan
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FrontEnd Developer | Javascript Enthusiast | Linux | Docker