nanoassert/index.js

Nanoscale assertion module

class AssertionError extends Error {
  name = 'AssertionError'
}

/**
 * Assert that `predicate` is truthy, otherwise throw `AssertionError` with optional `message`.
 * In Javascript runtimes that support `Error.captureStackTrace`, you will get a nicer stack trace with this error.
 *
 * @param  {unknown} predicate Value that must be truthy for the assertion to pass. 
 * @param  {string=} message Optional message to include in the error if the assertion fails.
 * @throws {AssertionError} If `predicate` is falsy.
 *
 * @example
 * assert(a !== b, `${a} !== ${b}`)
 */
module.exports = function assert (predicate, message) {
  if (!predicate) {
    const err = new AssertionError(message)
    Error.captureStackTrace?.(err, assert)
    throw err
  }
}