Registry / http-networking / condition-middleware

condition-middleware

library1.1.0jsnpmunverified

condition-middleware is an Express.js middleware utility that enables conditional execution of other middleware functions based on a runtime predicate. It allows developers to define complex branching logic within their Express route definitions, executing different middleware stacks depending on a boolean, numeric, or string-based condition evaluated against the request object. This approach streamlines the creation of dynamic request processing flows, avoiding cumbersome `if/else` statements directly in route handlers. The package currently stands at version 1.1.0 and ships with TypeScript types, facilitating its use in modern JavaScript and TypeScript projects. While a formal release cadence isn't specified, its current version indicates active maintenance. Its key differentiator is simplifying the composition of conditional middleware, which is a common pattern for authentication, authorization, or feature toggling, compared to manual conditional chaining or other more complex conditional middleware solutions.

http-networking web-framework auth-security

npm install condition-middleware

github ↗package ↗

INSTALL

IMPORT

SIG · CONDITION-MIDDLEWA

condition-middleware

http-networkingjavascriptv1.1.0

Install

—

Import

—

Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

condition

✓ import condition from 'condition-middleware';

✗ const condition = require('condition-middleware');

The library primarily uses ES module syntax for its default export. While CommonJS might work in some transpiled environments, native ESM is the intended usage. Ships with TypeScript types.

ConditionMiddlewareFunction

✓ import type { ConditionMiddlewareFunction } from 'condition-middleware';

Type import for advanced TypeScript usage, though the primary export is a function.

This quickstart demonstrates how to use `condition-middleware` to execute different Express middleware chains based on a dynamic boolean condition, such as a user's role extracted from request headers.

import express from 'express'; import condition from 'condition-middleware'; // Dummy middleware functions for demonstration const initialMiddleware = (req, res, next) => { console.log('Initial'); req.user = { role: 'guest' }; next(); }; const validateRequestAdmin = (req, res, next) => { console.log('Validating admin request'); next(); }; const otherMiddlewareAdmin = (req, res, next) => { console.log('Admin specific logic'); next(); }; const validateRequestOthers = (req, res, next) => { console.log('Validating other request'); next(); }; const otherMiddlewares = (req, res, next) => { console.log('Common middleware after condition'); next(); }; const finalMiddleware = (req, res, next) => { console.log('Final middleware'); res.send('Done!'); }; const errorMiddleware = (err, req, res, next) => { console.error('Error:', err.message); res.status(500).send('Server Error'); }; const app = express(); // Condition function that returns a boolean const isAdmin = (req) => { // Simulate different roles for demonstration const userRole = req.headers['x-user-role'] || 'guest'; req.user.role = userRole; console.log(`User role: ${req.user.role}`); return req.user.role === 'admin'; }; app.get( '/', initialMiddleware, condition(isAdmin)( [validateRequestAdmin, otherMiddlewareAdmin], // true path [validateRequestOthers] // false path ), otherMiddlewares, finalMiddleware, errorMiddleware ); app.listen(3000, () => { console.log('Server running on http://localhost:3000'); console.log('Test with:'); console.log('curl http://localhost:3000 -H "x-user-role: admin"'); console.log('curl http://localhost:3000'); });

Debug

Known issues

gotchaError-handling middlewares are not directly accepted inside a condition middleware chain. Standard error handling should occur outside the `condition` block.

fix

Place global or route-specific error-handling middleware after the `condition` block in the Express middleware chain.

affects: >=1.0.0

gotchaWhen using the object-based condition syntax, if the value returned by your condition function does not match any key in the provided object, no middleware within the conditional block will be executed.

fix

Ensure that your condition function's return values explicitly map to keys in the middleware object, or provide a default fallback mechanism in your logic.

affects: >=1.0.0

Errors

Common errors & fixes

TypeError: condition is not a function

Attempting to import the default ESM export using CommonJS `require` syntax, or incorrect named import.

fix

Use `import condition from 'condition-middleware';` for ESM. If using CommonJS, ensure your build system correctly transpiles or configure `module.exports = require('./dist/index').default;` in a wrapper.

Cannot read properties of undefined (reading 'role')

The condition function or a middleware inside the conditional block is attempting to access a property (e.g., `req.user.role`) that has not been initialized or is `undefined` on the `req` object.

fix

Ensure that any objects or properties accessed in your condition function (e.g., `req.user`) are properly initialized by preceding middlewares, or add null/undefined checks in your condition logic.

Upgrade

Version history

1.1.0latest on npm

Audit

Dependencies

expressrequiredThis package is an Express.js middleware and requires an Express application context to function. It is typically a peer dependency.

Agent activity

15 hits · last 30 days

node

OpenAI (training)

Resources

githubhttps://github.com/cenietob/conditional-middleware ↗

packagehttps://www.npmjs.com/package/condition-middleware ↗