babel-plugin-inline-constants

5.0.0 verified Sat Apr 25 auth: no javascript

Babel plugin (v5.0.0) to inline constant values from imported modules. Supports ESM (import) and CJS (require). Evaluates specified modules with Node to retrieve primitive values (numbers, strings, booleans, null) and replaces references directly in code for better gzip compression. TypeScript types included, ESM-only, Node 18+. Similar to babel-plugin-transform-define but focuses on module-exported constants.

Common errors

error Error: Cannot find module 'babel-plugin-inline-constants' ↓

cause Package not installed or installed as devDependency incorrectly.

fix

Run: npm install --save-dev babel-plugin-inline-constants

error TypeError: inlineConstants is not a function ↓

cause Using require on ESM-only module.

fix

Use import or ensure you are in an ESM context.

error Error: babel-plugin-inline-constants: missing required option 'modules' ↓

cause No modules option provided to the plugin.

fix

Example: { "plugins": [["babel-plugin-inline-constants", { "modules": ["./constants.js"] }]] }

error Error: Cannot read properties of undefined (reading 'some') ↓

cause Trying to inline a non-primitive export like an object or function.

fix

Only export primitives (numbers, strings, booleans, null) from constant modules.

error Module not found: Can't resolve './my-constants' ↓

cause Path resolution issue; module path relative to cwd.

fix

Ensure module path is correct relative to the Babel working directory.

Warnings

breaking Dropped support for Node 16. ↓

fix Upgrade to Node 18+.

breaking Migration to ESM-only. No CommonJS support. ↓

fix Use import syntax or dynamic import().

gotcha Modules are evaluated with Node, so only use the plugin if you trust the code. ↓

fix Do not inline untrusted modules.

gotcha The modules option is required; omitting it throws an error. ↓

fix Always specify modules in plugin options.

gotcha Only primitives (numbers, strings, booleans, null) are inlined. Objects, arrays, functions are not supported. ↓

fix Ensure constants are primitives.

Install

npm install babel-plugin-inline-constants

yarn add babel-plugin-inline-constants

pnpm add babel-plugin-inline-constants

Imports

default

wrong

const inlineConstants = require('babel-plugin-inline-constants')

correct

import inlineConstants from 'babel-plugin-inline-constants'

ESM-only since v2. CommonJS require is invalid.

Options

import type { Options } from 'babel-plugin-inline-constants'

TypeScript type import, not available as runtime value.

.babelrc plugin config

wrong

{
  "plugins": ["babel-plugin-inline-constants"]
}

correct

{
  "plugins": [["babel-plugin-inline-constants", { "modules": "./constants.js" }]]
}

The modules option is required. Omitting it will cause an error.

Quickstart

Shows how to configure the plugin with a modules list, and how constants are inlined in the output.

// .babelrc
{
  "plugins": [["babel-plugin-inline-constants", { "modules": ["./constants.js"] }]]
}

// constants.js
export const SITE = 'example.com';
export const PORT = 8080;

// input.js
import { SITE, PORT } from './constants.js';
console.log(`https://${SITE}:${PORT}`);

// output (after babel)
console.log(`https://example.com:8080`);