babel-plugin-unassert

3.2.0 verified Sat Apr 25 auth: no javascript

Babel plugin that removes assertion calls (assert, console.assert, power-assert) from production builds. Current stable version is 3.2.0, compatible with Babel 7. Release cadence is low, with major versions tied to Babel major versions. Key differentiator: allows full use of assertions during development without runtime overhead in production, with support for ES modules and power-assert integration. Alternative to manual conditional wrapping or dead-code elimination.

Common errors

error Error: Cannot find module 'babel-plugin-unassert' ↓

cause Package not installed or incorrectly required.

fix

Run 'npm install --save-dev babel-plugin-unassert' and ensure it's in node_modules.

error Error: [BABEL] unknown: Plugin babel-plugin-unassert is not a valid plugin (Error: Cannot find module 'babel-plugin-unassert') ↓

cause String name in Babel config but plugin not installed.

fix

Install the plugin and ensure node_modules path is correct. Check for typos.

error TypeError: babelPluginUnassert is not a function ↓

cause Trying to use the default export incorrectly, e.g., destructuring.

fix

Use const plugin = require('babel-plugin-unassert'); not const { unassert } = require('babel-plugin-unassert');

error Assertions not removed in production build ↓

cause Plugin not added to Babel plugins list, or NODE_ENV not set correctly.

fix

Add 'babel-plugin-unassert' to plugins array when NODE_ENV === 'production'. Verify Babel config applies during build.

Warnings

breaking Babel 7 is incompatible with Babel 6; babel-plugin-unassert v3 requires Babel 7. ↓

fix Use babel-plugin-unassert@2 for Babel 6, @1 for Babel <=5.

breaking Babel 6 is incompatible with Babel 5; babel-plugin-unassert v2 requires Babel 6. ↓

fix Use babel-plugin-unassert@1 for Babel 5 or lower.

deprecated babel-plugin-unassert v1 is deprecated; use v2 or v3 with appropriate Babel version. ↓

fix Upgrade to v2 (Babel 6) or v3 (Babel 7) as per your Babel version.

gotcha Plugin removes only calls to assert, console.assert, and power-assert modules. Custom assert functions are not removed. ↓

fix Ensure your assertions use standard assert module or power-assert. Alternatively, ensure custom functions have no side effects.

gotcha Using require('babel-plugin-unassert') in Node returns the plugin function, not an object with a default property. Importing with ES named import fails. ↓

fix Use require('babel-plugin-unassert') or import default. Never destructure as { unassert }.

Install

npm install babel-plugin-unassert

yarn add babel-plugin-unassert

pnpm add babel-plugin-unassert

Imports

default export

wrong

import { default } from 'babel-plugin-unassert'; const plugin = require('babel-plugin-unassert').default;

correct

import unassert from 'babel-plugin-unassert'; module.exports = { plugins: ['babel-plugin-unassert'] };

Plugin is a CommonJS module; use string name in Babel config or require() directly. No named exports.

require()

wrong

const { unassert } = require('babel-plugin-unassert'); const unassert = require('babel-plugin-unassert').unassert;

correct

const unassert = require('babel-plugin-unassert');

Only default export exists; destructuring or .unassert will be undefined.

ESM import (if bundler allows)
wrong
```
import { unassert } from 'babel-plugin-unassert'; import * as unassert from 'babel-plugin-unassert';
```
correct
```
import unassert from 'babel-plugin-unassert';
```
Package does not have a 'module' field; default import works if bundler resolves to CJS. Named import does not exist.

Quickstart

Demonstrates using babel-plugin-unassert via Babel config to remove assertions in production. Shows conditional plugin addition based on NODE_ENV.

// babel.config.js
module.exports = function (api) {
  const presets = ['@babel/env'];
  const plugins = [];

  if (process.env.NODE_ENV === 'production') {
    plugins.push('babel-plugin-unassert');
  }

  return {
    presets,
    plugins
  };
};

// src/math.js
const assert = require('assert');

function add(a, b) {
  console.assert(typeof a === 'number');
  assert(!isNaN(a));
  return a + b;
}

// After build:
// function add(a, b) {
//   return a + b;
// }