Overview

Documentation for @pencroff-lab/kore, a TypeScript core utilities library providing value-based error handling: the immutable Err type and flow, a tier of free functions over ResultTuple<T>.

Everything linked from this page ships inside the npm package. If you are reading this from node_modules/@pencroff-lab/kore/docs/, you are reading the documentation for the exact version you have installed — prefer it over the website when the two disagree.

Start here

import { Err, ok, fail, pipe, onOk, onErr, defaultTo } from "@pencroff-lab/kore";
import { expectOk, expectErr } from "@pencroff-lab/kore/test";

The package has two entry points: the root export carries the library, and @pencroff-lab/kore/test carries the assertion helpers so they never reach production bundles.

A ResultTuple<T> is readonly [T, null] | readonly [null, Err]. The error slot is the only failure signal — no operation inspects a value’s runtime shape. Every fallible callback returns a ResultTuple; map is the single exception, and its return is always data.

API reference

Generated from the source comments; regenerated on every release.

• Overview — every exported symbol
• flow — the primary API: free functions over ResultTuple<T>
• Err — immutable error type with wrapping, aggregation, codes, and JSON serialization
• test helpers — expectOk / expectErr, from the /test subpath
• Outcome — deprecated and frozen since v0.7.0
• Logger — structured, level-filtered logging
• dtStamp — compact, sortable date/time stamps

Guides

• Flow operation flows — creating results, exception boundaries, transformations, pipelines, combinators, terminal operations, serialization, input protection
• Error handling patterns — Err composition, propagation, and the nominal type guard
• Migration from throwing — step-by-step conversion from try/catch to result tuples
• Logging guide — levels, transports, conventions

Examples

Every example page is generated from an executable test file, so the code runs in the library’s own test suite.

• All examples
• flow examples
• Err examples
• test helper examples
• Outcome examples
• Logger examples
• dtStamp examples

Contributor documentation

These describe how the library itself is written; they are not needed to use the package.

• Documentation guide — the documentation layer model and budget rules
• TSDoc formatting rules

For agents

llms.txt at the package root is the machine-readable index of this documentation set. It links only to files that ship in the package.