elm-optimize-level-2

0.3.5 verified Fri May 01 auth: no javascript

A CLI tool (v0.3.5) that applies a second level of optimization to the JavaScript output of the Elm compiler, producing faster code while maintaining Elm semantics. It can be used as a drop-in replacement for `elm make --optimize` and supports an `--optimize-speed` flag for even faster code at the cost of ~5% larger bundle size. The project is experimental and may introduce breaking changes. Key differentiators: Elm-specific JS transformations (e.g., tweaking record updates), active development with community benchmarks, and no built-in minification.

Common errors

error Error [ERR_REQUIRE_ESM]: require() of ES Module ↓

cause The package is ESM-only and cannot be used with require() in CommonJS contexts.

fix

Use import or set "type": "module" in package.json.

error elm-optimize-level-2: command not found ↓

cause The package is not installed globally or not in PATH.

fix

Install globally: npm install -g elm-optimize-level-2 or use npx elm-optimize-level-2.

error elm-optimize-level-2: error: unrecognized argument: --help ↓

cause The CLI does not support --help; try --help?

fix

Check documentation or README; run without arguments to see usage (if supported).

Warnings

breaking elm-optimize-level-2 only generates JS files; it does not support HTML generation like `elm make`. ↓

fix Use a separate tool (e.g., elm-live) or serve the JS file with an HTML host.

deprecated The `--optimize-speed` flag may produce ~5% larger bundle sizes. Consider whether asset size or runtime performance is more important. ↓

fix Do not use `--optimize-speed` if bundle size is a constraint.

gotcha This package is experimental and may break your Elm code in unexpected ways. Run your test suite after each compilation. ↓

fix Only use in production after thorough testing.

gotcha Does not minify or gzip the output; you must do that separately before deployment. ↓

fix Use a minifier like Terser and gzip before deploying.

breaking Requires Node.js >= 16 and ES modules; does not support CommonJS. ↓

fix Set `"type": "module"` in your package.json or use `.mjs` extension.

Install

npm install elm-optimize-level-2

yarn add elm-optimize-level-2

pnpm add elm-optimize-level-2

Imports

default
wrong
```
const elmOptimizeLevel2 = require('elm-optimize-level-2')
```
correct
```
import { elmOptimizeLevel2 } from 'elm-optimize-level-2'
```
The package is ESM-only for Node >= 16 and ships TypeScript types. There is no CommonJS module export; using require() will fail.
CLI
wrong
```
npm run elm-optimize-level-2
```
correct
```
npx elm-optimize-level-2 Main.elm
```
The package is primarily a CLI tool. To use programmatically, import the default export and call it with options.
types
```
import type { OptimizeOptions } from 'elm-optimize-level-2'
```
TypeScript types are bundled; use type import for TypeScript projects.

Quickstart

Shows installation, CLI usage with output filename and --optimize-speed flag, and programmatic compilation using ESM import with TypeScript.

// Install globally
// $ npm install -g elm-optimize-level-2

// Then compile an Elm file:
// $ elm-optimize-level-2 Main.elm --output app.js

// Or with the --optimize-speed flag:
// $ elm-optimize-level-2 Main.elm --optimize-speed --output app.js

// Programmatic usage:
import elmOptimizeLevel2 from 'elm-optimize-level-2';
import { promises as fs } from 'fs';

async function compile() {
  const result = await elmOptimizeLevel2({
    entry: 'Main.elm',
    output: 'app.js',
    optimizeSpeed: false,
  });
  await fs.writeFile('app.js', result.code);
}

compile();