babel-preset-power-assert

3.0.0 verified Sat Apr 25 auth: no javascript

Babel preset for power-assert, providing a seamless integration to enable power-assert's enhanced assertion messages (full expression graph) in Node.js and browsers. The current stable version is 3.0.0, compatible with Babel 7. For Babel 6, use version 2.x. Released under MIT license. Maintained as part of the power-assert-js organization. Key differentiator: bundles babel-plugin-empower-assert and babel-plugin-espower, requiring only the preset and power-assert package as dependencies.

Common errors

error Error: Cannot find module 'babel-preset-power-assert' ↓

cause Missing package installation or incorrect npm install command.

fix

Run: npm install --save-dev babel-preset-power-assert

error TypeError: Cannot read property 'power-assert' of undefined ↓

cause Missing power-assert runtime package.

fix

Install power-assert: npm install --save-dev power-assert

error ReferenceError: assert is not defined ↓

cause power-assert module not imported in your test file.

fix

Add const assert = require('power-assert'); at the top of your file.

error Error: Requires Babel "7.0.0-0" but was loaded with "6.26.3" ↓

cause Using babel-preset-power-assert v3.x with Babel 6.

fix

Use babel-preset-power-assert@2.0.0 for Babel 6, or upgrade to Babel 7.

Warnings

breaking babel-preset-power-assert v3.x is incompatible with Babel 6. Use v2.x for Babel 6. ↓

fix Install babel-preset-power-assert@2.0.0 for Babel 6 projects.

deprecated babel-preset-power-assert v2.x is deprecated; use v3.x for Babel 7. ↓

fix Upgrade to v3.0.0 and update to Babel 7.

gotcha power-assert must be installed as a separate dependency; it is not included in the preset. ↓

fix Run: npm install --save-dev power-assert

gotcha The preset does not include '@babel/preset-env' or any other presets; you may need to combine with other presets in a Babel configuration. ↓

fix Add other presets (e.g., '@babel/preset-env') alongside 'power-assert'.

gotcha The preset only transforms assert statements; it does not provide the runtime 'power-assert' module. You must require/import 'power-assert' in your source files. ↓

fix Add const assert = require('power-assert'); (or import assert from 'power-assert') in files that use assert.

Install

npm install babel-preset-power-assert

yarn add babel-preset-power-assert

pnpm add babel-preset-power-assert

Imports

defaultPreset

wrong

// Wrong: using require('babel-preset-power-assert') directly as a function
var preset = require('babel-preset-power-assert');

correct

// In .babelrc or babel.config.js
{
  "presets": ["power-assert"]
}

The preset is used as a Babel preset string, not imported as a module in JavaScript code.

babel-plugin-empower-assert
wrong
```
const empowerAssert = require('babel-preset-power-assert').empowerAssert;
```
correct
```
import { empowerAssert } from 'babel-preset-power-assert';
```
This preset re-exports babel-plugin-empower-assert and babel-plugin-espower. However, direct import is not common; usually you just use the preset string.
babel-plugin-espower
wrong
```
const espower = require('babel-preset-power-assert').espower;
```
correct
```
import { espower } from 'babel-preset-power-assert';
```
Same as above. The plugins are exported for advanced usage, but the preset string is the recommended approach.

config

wrong

// Wrong: passing options as second argument to require
const preset = require('babel-preset-power-assert')(options);

correct

{
  "presets": [
    ["power-assert", {
      "empowerAssert": { /* options */ },
      "espower": { /* options */ }
    }]
  ]
}

Options are passed as an array entry in the presets list, not via function call.

Quickstart

Shows setup of babel-preset-power-assert with Babel, including installation, configuration, and a sample test using power-assert assert.

// 1. Install dependencies:
// npm install --save-dev babel-preset-power-assert power-assert

// 2. Create babel.config.js (or .babelrc):
module.exports = {
  presets: ['power-assert']
};

// 3. Write a test file (e.g., test.js):
const assert = require('power-assert');

describe('Array', () => {
  it('should have length 3', () => {
    const arr = [1, 2, 3];
    assert(arr.length === 3);
  });
});

// 4. Run with Babel:
// npx babel test.js --out-file test-transpiled.js && node test-transpiled.js