@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