@produck/type-error

A utility library for generating and throwing TypeError messages following the Produck TypeError template format.

Installation

npm install @produck/type-error

API

ErrorMessage(role: string, expected: string): string

Generates a formatted error message for type validation failures.

Parameters:

• role - Description of the parameter role (e.g., "args[0]", "options.name")
• expected - Expected type or value description (e.g., "string", "function")

Returns: Formatted error message string

Throws: TypeError if role or expected is not a string

Example:

import { ErrorMessage } from '@produck/type-error';

const message = ErrorMessage('args[0]', 'string');
// Returns: Invalid "args[0]", one "string" expected.

ThrowTypeError(role: string, expected: string): never

Throws a TypeError with a formatted message.

Parameters:

• role - Description of the parameter role
• expected - Expected type or value description

Throws: TypeError always with formatted message

Example:

import { ThrowTypeError } from '@produck/type-error';

function myFunction(value) {
  if (typeof value !== 'string') {
    ThrowTypeError('args[0]', 'string');
  }
}

AssertionChecker(validate: Validate, defaultExpected: string): Assert

Creates a reusable assertion function with a custom validation function.

Parameters:

• validate - Function that returns true if value is valid, false otherwise
• defaultExpected - Default "expected" message used in error messages

Returns: An assertion function (value: unknown, role: string, expected?: string) => undefined

Throws: TypeError if validate is not a function or defaultExpected is not a string

Example:

import { AssertionChecker } from '@produck/type-error';

const assertString = AssertionChecker(
  (value) => typeof value === 'string',
  'string'
);

// Use the assertion
try {
  assertString(42, 'args[0]');
} catch (error) {
  console.error(error.message);
  // TypeError: Invalid "args[0]", one "string" expected.
}

// With custom expected message
try {
  assertString(null, 'args[0]', 'non-null string');
} catch (error) {
  console.error(error.message);
  // TypeError: Invalid "args[0]", one "non-null string" expected.
}

Usage Patterns

Basic Validation

import { ThrowTypeError } from '@produck/type-error';

function processData(data) {
  if (typeof data !== 'object' || data === null) {
    ThrowTypeError('args[0]', 'object');
  }
  // ...
}

Creating Custom Validators

import { AssertionChecker } from '@produck/type-error';

const assertNumber = AssertionChecker(
  (v) => typeof v === 'number',
  'number'
);

const assertArray = AssertionChecker(
  (v) => Array.isArray(v),
  'array'
);

function calculateSum(numbers) {
  assertArray(numbers, 'args[0]');
  return numbers.reduce((sum, n) => {
    assertNumber(n, 'array element');
    return sum + n;
  });
}

License

MIT

Author

ChaosLee