Using a library in your webpack project? Here’s how to optimize it
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README.md

Optimize your libraries with webpack

Using a library in your webpack project? Use these tips to make your bundle smaller!

Want to add a tip? See the contribution guide and make a pull request!

Contents:

async

async is a collection of utilities for working with async functions. npm package

Generally, you should use the async-es package ⤵ instead. It ships with ES modules and is more optimized for bundling with webpack.

Still, even if prefer to use async, for the list of optimizations, see the async-es section ⤵.

async-es

async-es is a collection of utilities for working with async functions. It’s the same package as async, but it’s more optimized for bundling with webpack. npm package

Remove unused methods with babel-plugin-lodash

Safe to use by default / How to enable is ↓ / Added by @iamakulov

If you use async-es as a single import, you’re bundling the whole library into the application – even if you only use a couple of its methods:

// You only use `async.map`, but the whole library gets bundled
import async from 'async-es';

async.map(['file1', 'file2', 'file3'], fs.stat, function(err, results) {
  console.log(results);
});

Use babel-plugin-lodash to pick only those async-es methods you need:

// Before Babel is applied
import async from 'async-es';

async.map(['file1', 'file2', 'file3'], fs.stat, function(err, results) {
  console.log(results);
});

↓

// After Babel is applied
import _map from 'async-es/map';

_map(['file1', 'file2', 'file3'], fs.stat, function(err, results) {
  console.log(results);
});

Enable this plugin as follows:

// .babelrc
{
  "plugins": [["lodash", { "id": ["async-es"] }]],
}

babel-polyfill

babel-polyfill is a Babel’s package that loads core-js and a custom regenerator runtime. Babel docs · npm package

For the list of optimizations, see the core-js section ⤵.

core-js

core-js is a set of polyfills for ES5 and ES2015+. npm package

Remove unnecessary polyfills with babel-preset-env

Safe to use by default / How to enable / Added by @iamakulov

If you compile your code with Babel and babel-preset-env, add the useBuiltIns: true option. This option configures Babel to only include polyfills that are necessary for target browsers. I.e., if you target your app to support Internet Explorer 11:

// .babelrc
{
  "presets": [
    [
      "env",
      {
        "targets": {
          "browsers": ["last 2 versions", "ie >= 11"]
        }
      }
    ]
  ]
}

enabling useBuiltIns: true will remove polyfills for all features that Internet Explorer 11 already supports (such as Object.create, Object.keys and so on).

Ship non-transpiled code to modern browsers

Safe to use by default / How to enable / Added by @iamakulov

All browsers that support <script type="module"> also support modern JS features like async/await, arrow functions and classes. Use this feature to build two versions of the bundle and make modern browsers load only the modern code. For the guide, see the Philip Walton’s article.

date-fns

date-fns is a date utility library. npm package

Enable babel-plugin-date-fns

Safe to use by default / How to enable / Added by @chentsulin

babel-plugin-date-fns replaces full imports of date-fns with imports of specific date-fns functions:

import { format } from 'date-fns';
format(new Date(2014, 1, 11), 'MM/DD/YYYY');

import _format from 'date-fns/format';
_format(new Date(2014, 1, 11), 'MM/DD/YYYY');

lodash

Lodash is an utility library. npm package

Enable babel-plugin-lodash

Safe to use by default / How to enable / Added by @iamakulov

babel-plugin-lodash replaces full imports of Lodash with imports of specific Lodash functions:

import _ from 'lodash';
_.map([1, 2, 3], i => i + 1);

import _map from 'lodash/map';
_map([1, 2, 3], i => i + 1);

Note: the plugin doesn’t work with chain sequences – i.e. code like

_([1, 2, 3]).map(i => i + 1).value();

won’t be optimized.

Alias lodash-es to lodash

Safe to use by default / How to enable is ↓ / Added by @7rulnik

Some of your dependencies might use the lodash-es package instead of lodash. If that’s the case, Lodash will be bundled twice.

To avoid this, alias the lodash-es package to lodash:

// webpack.config.js
module.exports = {
  resolve: {
    alias: {
      'lodash-es': 'lodash',
    },
  },
};

Enable lodash-webpack-plugin

⚠ Use with caution / How to enable / Added by @iamakulov

lodash-webpack-plugin strips parts of Lodash functionality that you don’t need. For example, if you use _.get() but don’t need deep path support, this plugin can remove it. Add it to your webpack config to make the bundle smaller.

Use the plugin with caution. The default settings remove a lot of features, and your app might use some of them.

lodash-es

lodash-es is Lodash with ES imports and exports. npm package

For the list of optimizations, see the lodash section ⤴.

moment

Moment.js is a library for working with dates. npm package

Remove unused locales with moment-locales-webpack-plugin

⚠ Use with caution / How to enable / Added by @iamakulov

By default, Moment.js ships with 160+ minified KBs of localization files. If you app is only available in a few languages, you won’t need all these files. Use moment-locales-webpack-plugin to remove the unused ones.

Use the plugin with caution. The default settings remove all locales; this might break your app if you use some of them.

react

React is a library for building user interfaces. npm package

Remove propTypes declarations in production

Safe to use by default / How to enable / Added by @iamakulov

React doesn’t perform propTypes checks in production, but the propTypes declarations still occupy a part of the bundle. Use babel-plugin-transform-react-remove-prop-types to remove them from during building.

Migrate to an alternative React-like Library

⚠ Use with caution / Added by @iamakulov & @kurtextrem

There are alternatives to React with a similar API that have a smaller size or a higher performance, but lack some features (e.g., fragments, portals, or synthetic events).

  • Preact | The smallest React alternative (preact@8.3.1 + preact-compat@3.18.3 is 7.6 kB gzipped; react@16.4.0 + react-dom@16.4.0 is 31.4 kB gzipped) | No synthetic events | IE8 supported with polyfills

  • Nerv | Smaller than React, larger than Preact (nervjs@1.3.3 is 9.8 kB gzipped, compat is not neede; react@16.4.0 + react-dom@16.4.0 is 31.4 kB gzipped) | The goal of Nerv is to have 100% the same API (without Fiber and Suspense), see NervJS/nerv#10 for details | IE8 supported

  • Inferno | Smaller than React, larger than Preact and Nerv (inferno@5.4.2 + inferno-compat@5.4.2 is 11.3 kB gzipped; react@16.4.0 + react-dom@16.4.0 is 31.4 kB gzipped) | Higher runtime performance than React, the highest performance among all React alternatives, manual optimization possibilities offered | Partial synthetic events | IE8 unsupported natively

Migrate to alternatives with caution. Some of the alternatives don’t have synthetic events or are lacking some React 16 features (Preact issue, Inferno issue, Nerv issue). However, many projects still can be migrated without any codebase changes. See the migration guides: Preact, Inferno, Nerv.

reactstrap

Reactstrap is a Bootstrap 4 library for React. npm package

Remove unused modules with babel-plugin-transform-imports

Safe to use by default / How to enable is ↓ / Added by @kurtextrem

When you import a module from Reactstrap:

import { Alert } from 'reactstrap';

other Reactstrap modules also get bundled into the app and make it larger.

Use babel-plugin-transform-imports to strip unused modules:

// .babelrc
{
  "plugins": [
    ["transform-imports", {
      "reactstrap": {
        "transform": "reactstrap/lib/${member}",
        "preventFullImport": true
      }
    }]
  ]
}

To see how it works, check the babel-plugin-transform-imports section ⤵️.

react-bootstrap

react-bootstrap is a Bootstrap 3 library for React. npm package

Remove unused modules with babel-plugin-transform-imports

Safe to use by default / How to enable is ↓ / Added by @kurtextrem

When you import a module from react-bootstrap:

import { Alert } from 'react-bootstrap';

other react-bootstrap modules also get bundled into the app and make it larger.

Use babel-plugin-transform-imports to strip unused modules:

// .babelrc
{
  "plugins": [
    ["transform-imports", {
      "react-bootstrap": {
        "transform": "react-bootstrap/es/${member}",
        "preventFullImport": true
      }
    }]
  ]
}

To see how it works, check the babel-plugin-transform-imports section ⤵️.

react-router

React Router is a popular router solution for React. npm package

Remove unused modules with babel-plugin-transform-imports

Safe to use by default / How to enable is ↓ / Added by @kurtextrem

When you import a module from React Router:

import { withRouter } from 'react-router';

other React Router modules also get bundled into the app and make it larger.

Use babel-plugin-transform-imports to strip unused modules:

// .babelrc
{
  "plugins": [
    ["transform-imports", {
      "react-router": {
        "transform": "react-router/${member}",
        "preventFullImport": true
      }
    }]
  ]
}

(This was tested with React Router v4.)

To see how it works, check the babel-plugin-transform-imports section ⤵️.

styled-components

styled-components is a CSS-in-JS library. npm package

Minify the code with babel-plugin-styled-components

Safe to use by default / How to enable / Added by @iamakulov

There’s babel-plugin-styled-components that minifies the CSS code you write with styled-components. See the minification docs.

whatwg-fetch

whatwg-fetch is a complete window.fetch() polyfill. npm package

Replace with unfetch

⚠ Use with caution / How to migrate is ↓ / Added by @iamakulov

unfetch is a 500 bytes polyfill for window.fetch(). Unlike whatwg-fetch, it doesn’t support the full window.fetch() API, but instead focuses on polyfilling the most used parts.

Migrate to unfetch with caution. While it supports the most popular API parts, your app might break if it relies on something less common.

Solutions that work with multiple libraries

Of course, there are also optimization tips for other libraries too. You can use them with common sense to get smaller or more performant bundles.

babel-plugin-transform-imports

Safe to use by default / How to enable / Added by @kurtextrem / More Insight about this on Twitter

This handy babel plugin will transform your imports to only import specific components, which ensures not the whole library gets included (if tree-shaking is ineffective for the specific library).

// Before
import { Grid, Row, Col } from 'react-bootstrap';
// After
import Grid from 'react-bootstrap/lib/Grid';
import Row from 'react-bootstrap/lib/Row';
import Col from 'react-bootstrap/lib/Col';

License

Copyright 2018 Google Inc. All Rights Reserved. Licensed under the Apache License, Version 2.0.