dirty-chai

3.0.0 verified Fri May 01 auth: no javascript

A Chai plugin that converts terminating property assertions (e.g., .true, .ok) into function-call form (e.g., .true(), .ok()). This makes assertions lint-friendly (avoiding 'Expected an assignment or function call' warnings) and ensures assertions are actually invoked. Version 3.0.0 requires Chai >= 6.2.0 < 7. It works with browser and Node, and can adapt property assertions from other Chai plugins when loaded before them. Key differentiator: eliminates false positives from uninvoked property access.

Common errors

error TypeError: expect(...).to.be.true is not a function ↓

cause dirty-chai not installed or not used with chai.use()

fix

Install dirty-chai and call chai.use(dirtyChai) before using function-form assertions.

error AssertionError: expected [Function] to be true ↓

cause Assertion called without parentheses, returning the function instead of executing it

fix

Add parentheses to the assertion: .true() instead of .true

error Error: length is not a function ↓

cause Attempting to chain .length after another assertion (e.g., .exist.and.have.length)

fix

Use .length first in the chain or break into separate assertions.

Warnings

breaking dirty-chai 3.x requires Chai >= 6.2.0. Using older Chai versions will cause errors. ↓

fix Update chai to version >=6.2.0 <7

gotcha After dirty-chai, assertions must always be called with parentheses to execute. Syntactically correct without parens but assertion won't run. ↓

fix Always terminate chains with a function call, e.g., .true()

gotcha Chaining after .length or .arguments fails: these properties become functions and cannot be chained after other assertions. ↓

fix Use .length or .arguments first in the chain, or separate into multiple assertions

gotcha Plugin must be loaded after chai-as-promised (if used), but before other plugins to transform their property assertions. ↓

fix Load chai-as-promised before dirty-chai, and dirty-chai before any other plugins

deprecated CommonJS require is deprecated in v3; use ESM imports. ↓

fix Use import dirtyChai from 'dirty-chai' instead of require('dirty-chai')

Install

npm install dirty-chai

yarn add dirty-chai

pnpm add dirty-chai

Imports

dirtyChai

wrong

const dirtyChai = require('dirty-chai')

correct

import dirtyChai from 'dirty-chai'

ESM is the default module system since v3

chai
wrong
```
const chai = require('chai')
```
correct
```
import chai from 'chai'
```
Use ESM import for consistency with dirty-chai
use
wrong
```
chai.use(dirtyChai())
```
correct
```
chai.use(dirtyChai)
```
Plugin function must not be called; pass the function itself, not the result

Quickstart

Import and use dirty-chai with ESM, demonstrating function-call form for common assertions and custom error messages.

import chai from 'chai';
import dirtyChai from 'dirty-chai';

chai.use(dirtyChai);

const { expect } = chai;

expect(true).to.be.true();
expect(null).to.be.null('Custom error message');
expect([1]).to.be.empty();
expect('hello').to.exist();

// With chai-as-promised:
// import chaiAsPromised from 'chai-as-promised';
// chai.use(chaiAsPromised);
// chai.use(dirtyChai);