config-layer-lite

A layered configuration resolver — merges defaults, file config, environment overrides, and runtime overrides into one object, with source tracking per key.

Install

npm install config-layer-lite

Quick start

import { resolveConfig, buildStandardLayers } from 'config-layer-lite';

const layers = buildStandardLayers({
  defaults: { port: 3000, host: 'localhost' },
  file: { port: 4000 },
  env: { port: Number(process.env.PORT) || undefined },
  overrides: {}
});

const { values, sources } = resolveConfig(layers);
// values: { port: 4000 (or env value), host: 'localhost' }
// sources: { port: 'file' (or 'env'), host: 'defaults' }

Why config-layer-lite

Most apps load configuration from several places — hardcoded defaults, a config file, environment variables, and sometimes runtime flags — and the merge logic tends to get rewritten ad hoc each time, with no visibility into which source actually won for a given key. config-layer-lite makes the precedence explicit as an ordered list of named layers, skips undefined values so a layer can "not participate" for a key without clobbering an earlier one, and returns a sources map so you can debug or log exactly where each config value came from.

API

• resolveConfig(layers) — merges an ordered array of { name, values } layers (later wins) into { values, sources }.
• buildStandardLayers({ defaults, file, env, overrides }) — convenience builder for the common defaults → file → env → overrides stack, including only the layers you provide.

License

MIT