Did you know? # is the magic word to reduce your bundle size.

In modern JavaScript, prefixing a class field with # makes it private:

    class User {
      #token = 'secret';
    }

This isn’t just about access control. Bundlers like esbuild can safely rename #token to something shorter — like #a.

That means smaller bundles!

Compare this to public fields:

class User {
  token = 'secret';
}

Here, token must stay as-is — even in production — because external code might rely on it.

Private fields, on the other hand, are guaranteed to be internal-only.
That gives bundlers the green light to compress them aggressively.

In large apps with many classes, switching to # private fields can save a surprising amount of space — especially when field names are long.

Bonus: It’s not just about size.
Private fields make your APIs cleaner and your code more robust.

TL;DR:
Use # private fields.
Smaller bundles, safer code.

Gotcha:

• Supported in modern environments only.
• Can’t be accessed or tested from outside (even in unit tests) — by design!

Still, if you’re targeting evergreen browsers or bundling for modern platforms:

# is your friend.

If You Use node-redis in 2025, You Deserve the Bundle Size

Comments

[Saint Thomas Brown ♟]

Saving this one for the books, thanks for the read. Definitely will keep this in mind during my next project.

[Jay Lee]

Thanks, have a nice day :)

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