25 Feb 2025 2 min read

Boosting JavaScript Performance with import defer

The import defer proposal is an exciting development in the JavaScript world, offering a new way to manage module evaluation. By adopting this approach, we can optimize our applications, making them more efficient and responsive. Keep an eye on this proposal as it progresses—it might soon become a staple in our JavaScript toolkits!

What’s the Deal with import defer?

In JavaScript, when we import a module, its code runs immediately—this is known as eager evaluation. While this ensures all dependencies are ready to go, it can sometimes lead to unnecessary processing, especially if certain modules aren’t needed right away.

Enter import defer. This proposal suggests a way to delay a module’s evaluation until we actually use it. Think of it as lazy loading for your modules.

With this, the **utils module won’t run its code immediately** upon import. Instead, it’ll wait until you access something from it.

Then now it will download what need, because we are using it, his means you can import modules without the overhead of them executing right away, which can be a game-changer for performance.

Current Status and How to Experiment

As of February 2025, import defer is still a proposal under discussion by the TC39 committee, the folks who oversee JavaScript’s evolution. But if you’re eager to try it out, tools like Babel have got you covered. They offer a plugin that transforms import defer declarations into deferred require() calls, making it compatible with CommonJS environments.

@babel/plugin-proposal-import-defer · Babel

Transforms import defer declarations to deferred require() calls.

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