{"id":17116,"library":"middleware-utils","title":"Middleware Utils","description":"The `middleware-utils` package provides a compact collection of utility functions designed to streamline the creation and management of middleware in Node.js applications. It's particularly useful within build or templating ecosystems, such as `assemble`, where middleware often requires sequential or parallel execution. Key functionalities include `series` and `parallel` for controlling middleware flow, `error` and `handleError` for standardized error reporting, and `delims` for escaping and unescaping template delimiters. The package's current stable version is 1.0.0, originally released in 2017. Due to its age and lack of updates, it effectively has an abandoned release cadence. Its API is callback-based, reflecting the common asynchronous patterns of its era, and it lacks native support for modern JavaScript features like Promises or ES Modules.","status":"abandoned","version":"1.0.0","language":"javascript","source_language":"en","source_url":"https://github.com/jonschlinkert/middleware-utils","tags":["javascript","assemble","assembleutils","async","generate","middleware","route","routes","template"],"install":[{"cmd":"npm install middleware-utils","lang":"bash","label":"npm"},{"cmd":"yarn add middleware-utils","lang":"bash","label":"yarn"},{"cmd":"pnpm add middleware-utils","lang":"bash","label":"pnpm"}],"dependencies":[],"imports":[{"note":"This package is CommonJS-only. While a default import *might* work in some ESM environments via interoperability, direct named imports are not supported. Prefer `require`.","wrong":"const { utils } = require('middleware-utils');","symbol":"utils","correct":"import utils from 'middleware-utils';"},{"note":"Functions like `series` are properties of the default exported object, not named exports. Direct destructuring with `require` or `import` for these functions will fail.","wrong":"import { series } from 'middleware-utils';","symbol":"series","correct":"const utils = require('middleware-utils');\nconst seriesFn = utils.series;"},{"note":"Similar to `series`, `parallel` is accessed as a property of the main `utils` object.","wrong":"import { parallel } from 'middleware-utils';","symbol":"parallel","correct":"const utils = require('middleware-utils');\nconst parallelFn = utils.parallel;"}],"quickstart":{"code":"const utils = require('middleware-utils');\n\n// Simulate an application object that can register middleware\nconst app = {\n  _middleware: [],\n  preRender: function(pattern, fn) {\n    this._middleware.push({ pattern, fn });\n  },\n  // Simple handler to execute middleware\n  handle: function(view, done) {\n    const matchingFns = this._middleware.filter(m => view.name.match(m.pattern));\n    if (matchingFns.length === 0) {\n      return done(null, view);\n    }\n\n    const seriesRunner = utils.series(matchingFns.map(m => m.fn));\n    seriesRunner(view, done);\n  }\n};\n\nfunction createMiddleware(name) {\n  return function(file, next) {\n    console.log(`Executing middleware: ${name} for file: ${file.name}`);\n    // Simulate async work\n    setTimeout(() => next(), 50);\n  };\n}\n\n// Register middleware using utils.series\napp.preRender(/\\.hbs$/, utils.series([\n  createMiddleware('foo'),\n  createMiddleware('bar'),\n  createMiddleware('baz')\n]));\n\n// Register a single middleware\napp.preRender(/\\.txt$/, createMiddleware('text-processor'));\n\nconsole.log('Starting middleware processing...');\napp.handle({ name: 'template.hbs', content: '...' }, (err, result) => {\n  if (err) {\n    console.error('Error handling .hbs:', err);\n  } else {\n    console.log('Finished handling template.hbs.');\n  }\n});\n\napp.handle({ name: 'document.txt', content: '...' }, (err, result) => {\n  if (err) {\n    console.error('Error handling .txt:', err);\n  } else {\n    console.log('Finished handling document.txt.');\n  }\n});\n","lang":"javascript","description":"This example demonstrates how to use `middleware-utils.series` to run multiple middleware functions sequentially within a simulated application context, and how to define custom middleware functions."},"warnings":[{"fix":"For Node.js projects, use `const utils = require('middleware-utils');`. For modern ESM projects, consider using a module bundler that can handle CommonJS modules or alternative modern middleware utilities.","message":"The `middleware-utils` package is a CommonJS module and does not natively support ES Modules (`import`/`export` syntax). Attempting to use `import` statements directly will likely result in syntax errors or runtime issues in pure ESM environments.","severity":"breaking","affected_versions":">=1.0.0"},{"fix":"While still functional for its original purpose, developers should be aware of potential compatibility issues with newer Node.js versions or dependencies, and consider more actively maintained alternatives if possible.","message":"This package has not been updated since 2017 (v1.0.0) and is considered abandoned. It targets Node.js `>=4` and uses callback-based asynchronous patterns, which are less common in modern Node.js development that favors Promises and `async`/`await`.","severity":"gotcha","affected_versions":">=1.0.0"},{"fix":"Always access the utilities via the main imported object, e.g., `const utils = require('middleware-utils'); utils.series(...)`.","message":"The utility functions (`series`, `parallel`, `error`, `handleError`, `delims`) are exposed as properties of the main object returned by `require('middleware-utils')`. They are not individual named exports. Destructuring imports for these functions (`const { series } = require(...)`) will not work as expected and lead to runtime errors.","severity":"gotcha","affected_versions":">=1.0.0"},{"fix":"Wrap `middleware-utils` functions in Promises for better integration with modern async patterns. For example, `new Promise((resolve, reject) => utils.series(fns)(file, (err) => err ? reject(err) : resolve()));`.","message":"The callback-based API is a dated pattern. Modern Node.js applications heavily utilize Promises and `async`/`await` for asynchronous control flow. Integrating `middleware-utils` into a Promise-based codebase will require wrapping its callback functions in Promises.","severity":"deprecated","affected_versions":">=1.0.0"}],"env_vars":null,"last_verified":"2026-04-22T00:00:00.000Z","next_check":"2026-07-21T00:00:00.000Z","problems":[{"fix":"Change the import statement to `const utils = require('middleware-utils');` and access functions as properties, e.g., `utils.series(...)`.","cause":"Attempting to use ES module named import syntax (`import { series } from 'middleware-utils';`) for a CommonJS package that exports an object, not named functions.","error":"TypeError: (0, _middlewareUtils.series) is not a function"},{"fix":"Run `npm install middleware-utils` or `yarn add middleware-utils` to install the package. Double-check the spelling of the package name in your `require` statement.","cause":"The package is not installed in the project's `node_modules` directory, or there's a typo in the import path.","error":"Error: Cannot find module 'middleware-utils'"},{"fix":"Ensure all custom middleware functions passed to `utils.series` or `utils.parallel` properly accept a `next` callback as their last argument and call `next()` exactly once when their asynchronous operations are complete (or `next(err)` if an error occurs).","cause":"This error typically occurs within a middleware function when `next` (the callback to proceed to the next middleware) is either not passed correctly or is called after the middleware chain has already completed or encountered an error, leading to an invalid `next` reference.","error":"TypeError: next is not a function"}],"ecosystem":"npm","meta_description":null}