How darkgraycat/split-route works
Purpose and Entry Points
split-route is a small Node.js package for building conditional Express middleware chains within one route. Consumers import the package root (index.js), which exposes the implementation from lib/index.js.
Paths: index.js, lib/index.js, package.json
Public Builder API
The core export accepts a selector callback, typically (req, res) => value, and returns a fluent builder. Callers register branches with .case(value, ...middleware), optionally add .default(...middleware), then call .end() to obtain Express-compatible middleware.
Path: lib/index.js
Route Dispatch Stage
At request time, the built middleware invokes the selector callback and compares its result with registered case values. The selected branch becomes the active middleware sequence; if no case matches, the default branch is used when present.
Path: lib/index.js
Middleware Composition Boundary
Each branch accepts one or more Express middleware functions. The package’s primary boundary is between branch selection and normal Express execution: after selection, middleware must preserve Express’s (req, res, next) contract and call next() to continue the route pipeline.
Paths: lib/index.js, README.md
Nested Routing Composition
A branch can itself contain another completed splitRoute(...).case(...).end() middleware. This makes nested decision trees possible without creating separate Express route declarations; nesting remains standard middleware composition rather than a separate runtime or router abstraction.
Paths: lib/index.js, README.md
Runtime and Dependencies
The package runs in Node.js and targets Express middleware interoperability, but Express is consumed by applications rather than represented as repository infrastructure. There are no services, databases, web servers, or deployment resources in this repository.
Paths: package.json, package-lock.json
Verification Surface
Behavior is exercised through the package’s test entry point, covering the exported builder and its dispatch behavior.
Paths: tests/index.test.js, tests
Main entry points: lib/index.js Split-route builder · index.js Package root export · package.json Package manifest · README.md Usage documentation
Components 13
split-route package
Conditional Express middleware composition.
- Package root export · Public package entry point.
index.js - Split-route builder · Accepts a selector and exposes case, default, and end.
lib/index.js - Branch registry · Stores case values, middleware sequences, and an optional default.
lib/index.js - Completed middleware · Produced by end() for use in a route pipeline.
lib/index.js - Request dispatch · Matches the selector result to a case or default branch.
lib/index.js - Selected middleware chain · Runs the selected branch under the req, res, next contract.
lib/index.js - Nested completed split-route · A completed builder can be used as branch middleware.
lib/index.js - Package manifest · Defines the Node.js package runtime and dependencies.
package.json
Other components
- Express application · Imports the package and mounts completed middleware in a route.
- Selector callback · Derives the value used for branch selection.
- Express route pipeline · Continues when branch middleware calls next().
- Usage documentation · Documents middleware and nested composition.
README.md - Dispatch tests · Exercises the exported builder and dispatch behavior.
tests/index.test.js
Connections 16
- Express application → Package root export: imports
- Package root export → Split-route builder: exposes
- Split-route builder → Selector callback: accepts
- Split-route builder → Branch registry: registers cases and default
- Split-route builder → Completed middleware: end() returns
- Express application → Completed middleware: mounts in route
- Completed middleware → Request dispatch: invokes on request
- Selector callback → Request dispatch: provides selection value
- Branch registry → Request dispatch: supplies branches
- Request dispatch → Selected middleware chain: selects matching or default
- Selected middleware chain → Express route pipeline: calls next()
- Nested completed split-route → Selected middleware chain: can be included in
- Split-route builder → Nested completed split-route: can produce
- Usage documentation → Split-route builder: documents
- Dispatch tests → Split-route builder: verifies
- Package manifest → Package root export: declares entry package