Lodash: Importing only what you need

Lodash is a super popular utility library, but pulling in the entire thing when you only need a single function - like shuffle - is overkill. With modern bundlers like Vite, there are a few ways to keep your bundle size small.

Import styles matter

If you do this:

import _ from "lodash";

_.shuffle(array);

you're telling Vite (and Rollup under the hood) to grab the entire lodash library. That's ~70kb gzipped, even if you never touch debounce, cloneDeep, or any of the other helpers.

The right way

Instead, import just what you need:

import shuffle from "lodash/shuffle";

Now Rollup only includes the shuffle function and its tiny dependencies. Much better.

An even better option: lodash-es

The lodash team also publishes lodash-es. This is the exact same library, but distributed as ES modules.

Why does that matter? Because ES modules were designed with tree-shaking in mind. Tools like Rollup (which Vite uses in production builds) can safely drop any code you don't import.

As one StackOverflow thread puts it:

"CommonJS modules are not tree-shakable so you should definitely use
lodash-es, which is the Lodash library exported as ES Modules."

How to check your bundle

Want proof? Here are two easy ways:

1. Bundle visualizer
   Install the rollup-plugin-visualizer and add it to your vite.config.js. After running npm run build, you'll get a treemap showing exactly which parts of lodash made it in.

2. Compare build sizes
   Build your app twice:

   • once with import _ from "lodash"
   • once with import shuffle from "lodash-es/shuffle"

   Then compare the file sizes in your dist/assets/ folder. You'll see the difference right away.

Recap

• import _ from "lodash" → whole library
• import { shuffle } from "lodash" → whole library
• import shuffle from "lodash/shuffle" → just shuffle
• import shuffle from "lodash-es/shuffle" → best tree-shaking
  support

If you only need one function, don't ship 70kb of utilities you'll never use. Import smart, and your users' devices will thank you.