Migrating context-local variables in CommonJS

Examples in this chapter can be found here.

In CommonJS modules, there are several context-local variables that provide information about the current module and its execution context. When migrating to ESM, these variables need to be replaced with their ESM equivalents.

In Node.js, most of the replacements are provided through the import.meta object.

For older versions of Node.js where import.meta.filename and import.meta.dirname are not available, import.meta.url can be used to derive the filename and dirname using fileURLToPath() from node:url.

import { fileURLToPath } from 'node:url';
import { dirname } from 'node:path';
const __filename = fileURLToPath(import.meta.url);
const __dirname = dirname(__filename);

In the case of module and exports variables, writes to them typically are done to set up exports for the module, in which case these usually can be replaced with export statements. See Migrating exports for details. ESM does not support reflection on module exports, so reads from these variables have no direct replacements in ESM.