{"id":13352,"library":"iso-constants","title":"Isomorphic Node Constants","description":"The `iso-constants` package provides Node.js's `process.constants` values in a way that is usable across both Node.js and browser environments. It aims to offer a consistent set of system-level constants, such as `RTLD_LAZY` or `UV_THREADPOOL_SIZE`, regardless of the execution context. Currently at version `0.1.2`, the library maintains a generally low release cadence, primarily issuing patch fixes, indicating a stable and focused scope rather than rapid feature development. A key differentiator is its automatic constant update mechanism, which runs during `npm install` to ensure the most current constants are available. This approach enables developers to write isomorphic code that relies on these specific constants without needing conditional logic for different runtimes, simplifying cross-environment development.","status":"active","version":"0.1.2","language":"javascript","source_language":"en","source_url":"https://github.com/hugomrdias/iso-constants","tags":["javascript","constants","node","browser"],"install":[{"cmd":"npm install iso-constants","lang":"bash","label":"npm"},{"cmd":"yarn add iso-constants","lang":"bash","label":"yarn"},{"cmd":"pnpm add iso-constants","lang":"bash","label":"pnpm"}],"dependencies":[],"imports":[{"note":"Primary CommonJS import for the entire constants object.","symbol":"constants","correct":"const constants = require('iso-constants');"},{"note":"Correct ESM import for the default constants object. The package exports a single object, not named properties at the top level.","wrong":"import { constants } from 'iso-constants';","symbol":"constants","correct":"import constants from 'iso-constants';"},{"note":"Individual constants are properties of the main 'constants' object and are not directly exported as named imports from the package root.","wrong":"import { RTLD_LAZY } from 'iso-constants';","symbol":"RTLD_LAZY","correct":"import constants from 'iso-constants'; console.log(constants.RTLD_LAZY);"}],"quickstart":{"code":"import constants from 'iso-constants';\n\nconsole.log('--- Node.js System Constants ---');\nconsole.log('RTLD_LAZY:', constants.RTLD_LAZY);\nconsole.log('RTLD_NOW:', constants.RTLD_NOW);\nconsole.log('UV_THREADPOOL_SIZE:', constants.UV_THREADPOOL_SIZE);\n\n// This library ensures these Node.js process.constants are available\n// in both Node.js and browser environments, providing consistent values.\n\n// Example of a constant that might be platform-specific (e.g., Linux only)\nif (constants.hasOwnProperty('O_DIRECT')) {\n  console.log('O_DIRECT constant is available:', constants.O_DIRECT);\n} else {\n  console.log('O_DIRECT constant is not available (e.g., non-Linux platform).');\n}\n\n// Accessing another common constant\nconsole.log('F_OK (File exists flag):', constants.F_OK);\n","lang":"javascript","description":"Demonstrates how to import and access various Node.js `process.constants`, such as `RTLD_LAZY` and `UV_THREADPOOL_SIZE`, using `iso-constants` in an isomorphic way."},"warnings":[{"fix":"Pin exact package versions in your `package.json` and use `npm ci` or `yarn install --frozen-lockfile` to ensure reproducible builds from lock files.","message":"The package uses a `postinstall` script to fetch and update constants, which can lead to non-deterministic builds if the remote source changes between installs of the same package version. This also requires network access during `npm install`.","severity":"gotcha","affected_versions":">=0.1.0"},{"fix":"Review changelogs carefully for each update and test thoroughly, especially when upgrading between minor versions.","message":"As a `0.1.x` version, the API is not yet considered stable and breaking changes may occur in minor or even patch releases, contrary to semver conventions for `1.0.0`+ versions.","severity":"breaking","affected_versions":"<1.0.0"}],"env_vars":null,"last_verified":"2026-04-19T00:00:00.000Z","next_check":"2026-07-18T00:00:00.000Z","problems":[{"fix":"Change the import statement to `import constants from 'iso-constants';` in ESM files, or ensure your file is treated as CommonJS (e.g., by using `.cjs` extension or configuring `\"type\": \"commonjs\"` in your `package.json`).","cause":"Attempting to use CommonJS `require` syntax in an ESM module context (e.g., in a `.mjs` file or a file within a package with `\"type\": \"module\"` in `package.json`).","error":"ReferenceError: require is not defined"},{"fix":"Verify `iso-constants` is correctly installed by running `npm reinstall iso-constants` to re-execute the `postinstall` script. Check for any network errors or permission issues during the installation process.","cause":"The `constants` object was not successfully imported or initialized. This can happen if the `postinstall` script, which fetches the actual constant values, failed during `npm install`.","error":"TypeError: Cannot read properties of undefined (reading 'RTLD_LAZY') or similar 'constants' is undefined"}],"ecosystem":"npm","meta_description":null,"install_score":null,"install_tag":null,"quickstart_score":null,"quickstart_tag":null,"pypi_latest":null,"cli_name":null,"cli_version":null}