migrate

Lodash Migration & Compat Guide

Guide users through migrating lodash to es-toolkit and understanding the strict vs compat APIs, grounded in actual source code.

Input

$ARGUMENTS — Lodash code to migrate, specific function names, or a question about strict vs compat.

Core Concepts

es-toolkit (strict): Opinionated, simplified API for the 85% use case. Smaller bundle, may differ from lodash in edge cases by design. New functions are added here.

es-toolkit/compat: Aims for full lodash test compatibility within a defined scope. See docs/compatibility.md for out-of-scope behaviors (e.g., implicit type conversions, prototype modifications).

Why source-first matters

The only reliable way to know the difference between strict and compat is to inspect the version installed in the user's project. The skill may be installed as a standalone directory, so never assume the es-toolkit repository or a sibling docs directory is available.

Workflow

If a specific function or lodash code is given

1. Identify lodash functions from input

Extract which lodash functions are used and how they're imported.

2. Verify availability in the installed package

Run from the package that depends on es-toolkit. In a monorepo this is usually a workspace package, not the repository root. If the project uses Yarn Plug'n'Play, use yarn node instead of node.

Replace the example names with the lodash functions found in the input:

node --input-type=module -e "
import { createRequire } from 'node:module';

const require = createRequire(import.meta.url);
const names = ['get', 'chunk', 'map'];
const pkg = require('es-toolkit/package.json');
const entries = Object.keys(pkg.exports)
  .filter(subpath => subpath !== './package.json' && !subpath.includes('*'))
  .map(subpath => subpath === '.' ? 'es-toolkit' : 'es-toolkit/' + subpath.slice(2));
const modules = await Promise.all(entries.map(entry => import(entry).catch(() => null)));
if (modules.every(module => module == null)) {
  console.error('es-toolkit is not resolvable from ' + process.cwd());
  process.exit(1);
}
for (const name of names) {
  const found = entries.filter((_, index) => modules[index] != null && name in modules[index]);
  console.log(name.padEnd(20), found.join(', ') || 'NOT AVAILABLE');
}
"