Level

Level is the entry-point package of the Level ecosystem: a universal, embeddable key-value database that exposes the same abstract-level API in Node.js (backed by classic-level, a Node-API binding to LevelDB) and in browsers (backed by browser-level, which wraps IndexedDB). It gives JavaScript and TypeScript applications a single, lexicographically-sorted key-value store abstraction that works identically whether the code runs on a server, in Electron, or in a web page.

Because the package only swaps its backing implementation per environment (via package.json’s browser field), application code never has to branch on platform: the same put, get, del, batch, and async-iterator calls work everywhere, making Level a common building block for embedded databases, caches, and higher-level stores (sublevels, encodings, and a large ecosystem of level-* modules) built on top of it.

What You Get

• A single Level class whose constructor and methods (put, get, getMany, del, batch, iterator, keys, values) work identically in Node.js and browsers
• Automatic backend selection at install/bundle time — classic-level/LevelDB on Node.js, browser-level/IndexedDB in the browser — via the standard browser field in package.json
• Full TypeScript type declarations covering the common surface between the Node.js and browser backends, with generics for custom key/value types
• Support for binary keys and values (Buffer/Uint8Array) as well as strings, plus pluggable encodings (e.g. JSON) via valueEncoding/keyEncoding options
• Sublevel support inherited from abstract-level, allowing a single database to be partitioned into isolated, prefixed namespaces
• Async iterator support (for await...of) for range queries over keys and values with gt/lt/gte/lte bounds

Common Use Cases

• Embedded local storage for a desktop Electron app that needs the same persistence code to also run in a browser build
• A lightweight, dependency-light key-value store for Node.js CLI tools, servers, or scripts that don’t need a full external database
• Foundation layer for higher-level Level ecosystem modules (e.g. level-transcoder, subleveldown-style sublevels, many-level) that build indexing, replication, or querying on top
• Offline-first web applications that persist structured data client-side via IndexedDB without writing IndexedDB code directly

Under The Hood

Architecture - Level is deliberately not an implementation but a thin dispatch layer: index.js re-exports classic-level’s ClassicLevel as Level, while browser.js re-exports browser-level’s BrowserLevel under the same name; bundlers and Node’s require resolve to the right file automatically via the browser field in package.json. All real behavior — LevelDB bindings on Node.js, IndexedDB wrapping in browsers, encoding, sublevels, iterators — lives in abstract-level (the shared interface both backends implement) and its two concrete implementations, which Level simply aliases. This zero-logic dispatch pattern is the entire architecture: one class name, two backends, selected by environment.

Tech Stack - The package has three runtime dependencies (abstract-level@^3.1.0, browser-level@^3.0.0, classic-level@^3.0.0), all from the same Level GitHub organization, and no other production code. Types are hand-written in index.d.ts, importing and intersecting the type surfaces of abstract-level, classic-level, and browser-level so consumers get one unified typed API. Development tooling uses standard for linting, tape for tests, nyc for coverage, and airtap/Playwright for cross-browser testing, targeting Node.js 18+ per the engines field.

Code Quality - test.js is a single 12-line smoke test (put/get roundtrip via tape) with an explicit comment explaining why: since Level directly re-exports classic-level/browser-level without wrapping logic, the substantive test coverage lives in those downstream packages, not here. CI runs the smoke test across Node 18/20/22 and, on Node 22, also runs the browser test suite via Playwright and reports coverage to Codecov. This is a deliberately minimal-surface-area design: with effectively zero original logic, there is little to unit test beyond confirming the correct backend loads.

API Design - The public API is a single Level class extending AbstractLevel, so developers already familiar with any other abstract-level-based store (or with LevelDB/IndexedDB concepts generally) get a zero-boilerplate new Level(location, options) constructor and immediately usable put/get/del/batch/iterator methods, including native async-iterator support (for await...of db.iterator()). TypeScript generics (Level<KDefault, VDefault>) let consumers set default key/value types once. The README documents the constructor and defers to classic-level/browser-level READMEs for backend-specific options, keeping the top-level docs short but requiring a two-hop lookup for advanced options.