Metreeca/Core

A lightweight library of core TypeScript utilities.

@metreeca/core is a zero-dependency foundation for type-safe operations, data validation, and functional programming, providing utilities for type guards, safe casts, comparisons, immutability, data manipulation, and error handling.

Installation

npm install @metreeca/core
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Usage

Runtime Guards

Type guards for runtime JavaScript types and protocols.

import { isDefined, isEmpty, isFunction, isPromise, isIterable } from '@metreeca/core';

if ( isDefined(value) ) { /* value is T */ }

isEmpty({}); // true
isEmpty([]); // true

isFunction(() => {}); // true
isPromise(Promise.resolve(42)); // true
isIterable([1, 2, 3]); // true
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Value Guards

Type guards for JSON-like values and data structures.

import { isBoolean, isNumber, isString, isObject, isArray } from '@metreeca/core';

isBoolean(true); // true
isNumber(42); // true (excludes NaN, Infinity)
isString('hello'); // true

isObject({ a: 1 }); // true
isObject(new Date()); // false

isArray([1, 2, 3], isNumber); // true
isArray([1, 'two'], isNumber); // false
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Value Casts

Safe type casts returning undefined instead of throwing.

import { asNumber, asString, asObject, asArray } from '@metreeca/core';

asNumber(42); // 42
asNumber('42'); // undefined
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Structural Utilities

Deep operations on complex types.

import { equals, immutable } from '@metreeca/core';

equals({ a: [1, 2] }, { a: [1, 2] }); // true
immutable({ a: [1, 2, 3] }); // deep frozen
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Error Utilities

Throw errors in expression contexts.

import { error } from '@metreeca/core';

isValid(input) ? input : error('Invalid input');
findUser(id) ?? error(`User ${id} not found`);
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Support

• open an issue to report a problem or to suggest a new feature
• start a discussion to ask a how-to question or to share an idea

License

This project is licensed under the Apache 2.0 License – see LICENSE file for details.