Installation

Requirements

• Node.js 18+ / Bun 1+ / Deno 1.38+
• TypeScript 5.0+

lodash is a regular runtime dependency — your package manager installs it for you.

Package managers

npm

npm install assertcheck

yarn

yarn add assertcheck

pnpm

pnpm add assertcheck

bun

bun add assertcheck

JSR (Deno / Bun / npm)

The package is published on JSR under the @thonymg scope.

deno add jsr:@thonymg/assertcheck
bunx jsr add @thonymg/assertcheck
npx jsr add @thonymg/assertcheck

When installed from JSR, import from @thonymg/assertcheck:

import { assert, check } from "@thonymg/assertcheck"

Entry points

import { assert, check, AssertionError } from "assertcheck"   // everything you need
import type { AssertOptions } from "assertcheck"              // the opts type

Formatting primitives for custom assertions are exported from the same root: buildBlock, fmtValue, diffObjects, color, output, parseOpts.

TypeScript config

Any modern moduleResolution (bundler, node16, nodenext) works. Enable strict to get the full benefit of type narrowing.

{
  "compilerOptions": {
    "strict": true,
    "module": "ESNext",
    "moduleResolution": "bundler"
  }
}

Verify the install

import { assert } from "assertcheck"

assert.equal(1, 1) // passes silently
assert.equal(1, 2) // prints a formatted block and throws AssertionError

There is nothing to configure. Assertions are always enabled, in every environment.