This team is spun off from the[Modules team](https://github.com/nodejs/modules). We aim to implement the[use cases](https://github.com/nodejs/modules/blob/main/doc/use-cases.md) that went unfulfilled by the initial ES modules implementation that can be achieved vialoaders.

This team is spun off from the[Modules team](https://github.com/nodejs/modules). We aim to implement the[use cases](https://github.com/nodejs/modules/blob/main/doc/use-cases.md) that went unfulfilled by the initial ES modules implementation that can be achieved viamodule customization hooks; to provide hooks that are sufficiently powerful to allow the sunset of CommonJS monkey-patching; and to improve the ES modules implementation to reach parity with CommonJS.

Before extending into new frontiers, we need to improvetheloaders API enoughthatuserscando just about everything they could doinCommonJS with ESM + loaders. (Outside of loaders scope, but related tothegoal of parity between CommonJS and ESM, is finishing and stabilizing`--experimental-vm-modules`.)

-[ ] Synchronous version ofthemodule customization hooks sothatthe hookscanbe usedinthe`require` path onthemain thread, per[design](./doc/design/proposal-synchronous-hooks.md).

-[x] Refactor theinternal Node ESMLoader hooks into`resolve` and`load`. Node’s internalloader already has no-ops for`transformSource` and`getGlobalPreloadCode`, so all this really entails is wrapping the internal`getFormat`and`getSource` with one function`load` (`getFormat` is used internally outside ESMLoader, so they cannot merely be merged).https://github.com/nodejs/node/pull/37468

-[ ] Synchronize theESMloader, to hopefully close the startup performance gap with CommonJSandallow more predictable async activity on startup (for example, no`async_hooks` activity will precede user code).[Tracking issue](https://github.com/nodejs/node/issues/55782).

-[x] Implement chaining as described in the[design](doc/design/proposal-chaining-middleware.md), where the`default<hookName>` becomes`next` and references the next registered hook in the chain.https://github.com/nodejs/node/pull/42623

-[x] Have loaders apply to subsequent loaders.https://github.com/nodejs/loaders/blob/main/doc/design/proposal-ambient-loaders.md,https://github.com/nodejs/node/pull/43772

-[x] Move loaders off thread.https://github.com/nodejs/modules/issues/351#issuecomment-634347749.https://github.com/nodejs/node/issues/43658,https://github.com/nodejs/node/pull/44710

-[x] Provide a way to register loaders from application code, such as`import { register } from 'node:module'`.https://github.com/nodejs/node/pull/46826,https://github.com/nodejs/node/pull/48559.

-[x] Replace`globalPreload` hook with new`initialize` hook; update`register` to preserve the communications channel from that hook so that we continue to provide a way to communicate between loaders code and application code. Seehttps://github.com/nodejs/loaders/discussions/124#discussioncomment-5735397 andhttps://github.com/nodejs/loaders/issues/147.https://github.com/nodejs/node/pull/48842.

-[x] Remove`globalPreload` hook.https://github.com/nodejs/node/pull/49144.

-[x] Support loading source when the return value of`load` has`format: 'commonjs'`. Seehttps://github.com/nodejs/node/issues/34753#issuecomment-735921348 andhttps://github.com/nodejs/loaders-test/blob/835506a638c6002c1b2d42ab7137db3e7eda53fa/coffeescript-loader/loader.js#L45-L50.https://github.com/nodejs/node/pull/47999.

-[x] Unflag`import.meta.resolve`.https://github.com/nodejs/node/pull/49028.

-[x] Provide a way to register loaders via configuration, for example via adding support for`.env` files to Node.js or having`node` read configuration from a new field in`package.json` or other configuration file. Seehttps://github.com/nodejs/node/pull/46826,[#98](https://github.com/nodejs/loaders/issues/98),https://github.com/nodejs/node/pull/43973#issuecomment-1249549346.https://github.com/nodejs/node/pull/48890.

-[ ] Integrated support for external formats.

-[ ] Phase 1: Support identifying external modules (eg`typescript`); seehttps://github.com/nodejs/node/pull/49704.

-[ ] Phase 2: Support guided remediation via package manager search (eg`npm search … typescript`).

-[ ] Phase 3: Automatically configure Node.

-[ ] First-class support for[import maps](https://github.com/WICG/import-maps) that doesn’t require a custom loader.

-[ ] Hooks for customizing the REPL, including transpilation and tab completion. Support users pasting TypeScript (or CoffeeScript or whatever) into the REPL and having just as good an experience as with plain JavaScript.

-[ ] Support top-level`await` in the REPL API, if possible.

-[ ] Allow customizing string inputs:`--eval` CLI flag,`Worker` constructor, stdin, etc.

-[ ] Hooks for customizing the stack trace (in other words, a hook version of`Error.prepareStackTrace`). This would allow transpiled languages to improve the output.

This is the legacy roadmap as it was in 2024:

Before extending into new frontiers, we need to improve the loaders API enough that users can do just about everything they could do in CommonJS with ESM + loaders. (Outside of loaders scope, but related to the goal of parity between CommonJS and ESM, is finishing and stabilizing`--experimental-vm-modules`.)

-[x] Finishhttps://github.com/nodejs/node/pull/37468 /https://github.com/nodejs/node/pull/35524, simplifying the hooks to`resolve`,`load` and`globalPreloadCode`.

-[x] Refactor the internal Node ESMLoader hooks into`resolve` and`load`. Node’s internal loader already has no-ops for`transformSource` and`getGlobalPreloadCode`, so all this really entails is wrapping the internal`getFormat` and`getSource` with one function`load` (`getFormat` is used internally outside ESMLoader, so they cannot merely be merged).https://github.com/nodejs/node/pull/37468

-[x] Refactor Node’s internal ESM loader to move its exception on unknown file types from within`resolve` (on detection of unknown extensions) to within`load` (if the resolved extension has no defined translator).https://github.com/nodejs/node/pull/37468

-[x] Implement chaining as described in the[design](doc/design/proposal-chaining-middleware.md), where the`default<hookName>` becomes`next` and references the next registered hook in the chain.https://github.com/nodejs/node/pull/42623

-[x] Have loaders apply to subsequent loaders.https://github.com/nodejs/loaders/blob/main/doc/design/proposal-ambient-loaders.md,https://github.com/nodejs/node/pull/43772

-[x] Move loaders off thread.https://github.com/nodejs/modules/issues/351#issuecomment-634347749.https://github.com/nodejs/node/issues/43658,https://github.com/nodejs/node/pull/44710

-[x] Provide a way to register loaders from application code, such as`import { register } from 'node:module'`.https://github.com/nodejs/node/pull/46826,https://github.com/nodejs/node/pull/48559.

-[x] Replace`globalPreload` hook with new`initialize` hook; update`register` to preserve the communications channel from that hook so that we continue to provide a way to communicate between loaders code and application code. Seehttps://github.com/nodejs/loaders/discussions/124#discussioncomment-5735397 andhttps://github.com/nodejs/loaders/issues/147.https://github.com/nodejs/node/pull/48842.

-[x] Remove`globalPreload` hook.https://github.com/nodejs/node/pull/49144.

-[x] Support loading source when the return value of`load` has`format: 'commonjs'`. Seehttps://github.com/nodejs/node/issues/34753#issuecomment-735921348 andhttps://github.com/nodejs/loaders-test/blob/835506a638c6002c1b2d42ab7137db3e7eda53fa/coffeescript-loader/loader.js#L45-L50.https://github.com/nodejs/node/pull/47999.

-[x] Unflag`import.meta.resolve`.https://github.com/nodejs/node/pull/49028.

-[x] Provide a way to register loaders via configuration, for example via adding support for`.env` files to Node.js or having`node` read configuration from a new field in`package.json` or other configuration file. Seehttps://github.com/nodejs/node/pull/46826,[#98](https://github.com/nodejs/loaders/issues/98),https://github.com/nodejs/node/pull/43973#issuecomment-1249549346.https://github.com/nodejs/node/pull/48890.

-[ ] Integrated support for external formats.

-[ ] Phase 1: Support identifying external modules (eg`typescript`); seehttps://github.com/nodejs/node/pull/49704.

-[ ] Phase 2: Support guided remediation via package manager search (eg`npm search … typescript`).

-[ ] Phase 3: Automatically configure Node.

-[ ] First-class support for[import maps](https://github.com/WICG/import-maps) that doesn’t require a custom loader.

-[ ] Add helper/utility functions to reduce boilerplate in user-defined hooks.

-[ ] Start with helpers for retrieving the closest parent`package.json` associated with a specifier string; and for retrieving the`package.json` for a particular package by name (which is not necessarily the same result).

-[ ] Potentially include all the functions that make up the ESM resolution algorithm as defined in the[spec](https://nodejs.org/api/esm.html#resolution-algorithm-specification). Create helper functions for each of the functions defined in that psuedocode:`esmResolve`,`packageImportsResolve`,`packageResolve`,`esmFileFormat`,`packageSelfResolve`,`readPackageJson`,`packageExportsResolve`,`lookupPackageScope`,`packageTargetResolve`,`packageImportsExportsResolve`,`patternKeyCompare`. (Not necessarily all with these exact names, but corresponding to these functions from the spec.)

-[ ] Follow up with similar helper functions that make up what happens within Node’s internal`load`. (Definitions to come.)

-[ ] Helper/utility functions to allow access to the CommonJS named exports discovery algorithm (`cjs-module-lexer`).

-[ ] Hooks for customizing the REPL, including transpilation and tab completion. Support users pasting TypeScript (or CoffeeScript or whatever) into the REPL and having just as good an experience as with plain JavaScript.

-[ ] Support top-level`await` in the REPL API, if possible.

-[ ] Allow customizing string inputs:`--eval` CLI flag,`Worker` constructor, stdin, etc.

-[ ] Hooks for customizing the stack trace (in other words, a hook version of`Error.prepareStackTrace`). This would allow transpiled languages to improve the output.

-[ ] Hooks for customizing filesystem calls, for allowing things like virtual filesystems or archives treated as volumes.

-[ ] Inherit configuration blob to worker threads and child processes.