Installation

Package managersCopy Anchor Link

npm install mutative

Mutative has no dependencies. A production bundle of create alone is about 7.9 kB after Brotli compression, and one of create, apply, current and original about 8.5 kB, including patches, Map and Set support and native array methods, which need no plugins.

import { create } from 'mutative';

RequirementsCopy Anchor Link

• JavaScript. Mutative needs Proxy and the ES2018 syntax that its builds keep, such as object spread: Node.js 14.0 or later, current browsers, and React Native 0.64 or later. Engines that support Proxy but not ES2018 syntax, such as Chrome 49–59, Firefox 18–54, Safari 10–11.0 and Edge 12–18, need Mutative transpiled by your build. Internet Explorer has no Proxy and is not supported.
• TypeScript. The type declarations support TypeScript 5.0 and later; see TypeScript.

Development and production buildsCopy Anchor Link

The package holds a development build, with full error messages, warnings and extra checks, and a minified production build, whose errors are numeric codes. Which one runs depends on process.env.NODE_ENV:

• Bundlers resolve the ESM build, whose development checks compare process.env.NODE_ENV with 'production'. Bundlers that define it as 'production', as webpack, Vite, Rollup and esbuild setups for production usually do, drop the development code. Bundles that target Node.js resolve the CommonJS entry instead; define process.env.NODE_ENV there, or leave Mutative external.
• Node.js runs the CommonJS build for require and import alike, and selects the development or production build from NODE_ENV when it loads Mutative.
• Browsers without a bundler have no process, so they need the production ESM file or the UMD build below.

CDNCopy Anchor Link

• Unpkg: <script src="https://unpkg.com/mutative"></script>
• JSDelivr: <script src="https://cdn.jsdelivr.net/npm/mutative"></script>
• ES module: import { create } from 'https://unpkg.com/mutative/dist/mutative.esm.production.min.mjs';

The <script> tags load the production UMD build, which defines a global Mutative, as in Mutative.create(baseState, recipe). The package's other ESM files read process.env.NODE_ENV, which bundlers and Node.js provide; a browser without a bundler needs the production file above.

<script type="module">
  import { create } from 'https://unpkg.com/mutative/dist/mutative.esm.production.min.mjs';

  const state = create({ count: 0 }, (draft) => {
    draft.count += 1;
  });
  console.log(state.count); // 1
</script>