Workspaces is a generic term that refers to the set of features in the npm cli that provides support for managing multiple packages from your local file system from within a singular top-level, root package.

This set of features makes up for a much more streamlined workflow handling linked packages from the local file system. It automates the linking process as part of npm install and removes the need to manually use npm link in order to add references to packages that should be symlinked into the current node_modules folder.

We also refer to these packages being auto-symlinked during npm install as a single workspace, meaning it's a nested package within the current local file system that is explicitly defined in the package.json \(la/configuring-npm/package-json#workspaces\(ra workspaces configuration.

Workspaces are usually defined via the workspaces property of the package.json \(la/configuring-npm/package-json#workspaces\(ra file, e.g:

{
 "name": "my-workspaces-powered-project",
 "workspaces": \[lB]
 "packages/a"
 \[rB]
}

Given the above package.json example living at a current working directory . that contains a folder named packages/a that itself contains a package.json inside it, defining a Node.js package, e.g:

.
+-- package.json
`-- packages
 +-- a
 | `-- package.json

The expected result once running npm install in this current working directory . is that the folder packages/a will get symlinked to the node_modules folder of the current working dir.

Below is a post npm install example, given that same previous example structure of files and folders:

.
+-- node_modules
| `-- a -> ../packages/a
+-- package-lock.json
+-- package.json
`-- packages
 +-- a
 | `-- package.json

You may automate the required steps to define a new workspace using npm help init. For example in a project that already has a package.json defined you can run:

npm init -w ./packages/a

This command will create the missing folders and a new package.json file (if needed) while also making sure to properly configure the "workspaces" property of your root project package.json.

It's possible to directly add/remove/update dependencies of your workspaces using the workspace config \(la/using-npm/config#workspace\(ra.

For example, assuming the following structure:

.
+-- package.json
`-- packages
 +-- a
 | `-- package.json
 `-- b
 `-- package.json

If you want to add a dependency named abbrev from the registry as a dependency of your workspace a, you may use the workspace config to tell the npm installer that package should be added as a dependency of the provided workspace:

npm install abbrev -w a

Note: other installing commands such as uninstall, ci, etc will also respect the provided workspace configuration.

Given the specifics of how Node.js handles module resolution \(lahttps://nodejs.org/dist/latest-v14.x/docs/api/modules.html#modules_all_together\(ra it's possible to consume any defined workspace by its declared package.json name. Continuing from the example defined above, let's also create a Node.js script that will require the workspace a example module, e.g:

// ./packages/a/index.js
module.exports = 'a'

// ./lib/index.js
const moduleA = require('a')
console.log(moduleA) // -> a

When running it with:

node lib/index.js

This demonstrates how the nature of node_modules resolution allows for workspaces to enable a portable workflow for requiring each workspace in such a way that is also easy to npm help publish these nested workspaces to be consumed elsewhere.

You can use the workspace configuration option to run commands in the context of a configured workspace. Additionally, if your current directory is in a workspace, the workspace configuration is implicitly set, and prefix is set to the root workspace.

Following is a quick example on how to use the npm run command in the context of nested workspaces. For a project containing multiple workspaces, e.g:

.
+-- package.json
`-- packages
 +-- a
 | `-- package.json
 `-- b
 `-- package.json

By running a command using the workspace option, it's possible to run the given command in the context of that specific workspace. e.g:

npm run test --workspace=a

You could also run the command within the workspace.

cd packages/a && npm run test

Either will run the test script defined within the ./packages/a/package.json file.

Please note that you can also specify this argument multiple times in the command-line in order to target multiple workspaces, e.g:

npm run test --workspace=a --workspace=b

Or run the command for each workspace within the 'packages' folder:

npm run test --workspace=packages

It's also possible to use the workspaces (plural) configuration option to enable the same behavior but running that command in the context of all configured workspaces. e.g:

npm run test --workspaces

Will run the test script in both ./packages/a and ./packages/b.

Commands will be run in each workspace in the order they appear in your package.json

{
 "workspaces": \[lB] "packages/a", "packages/b" \[rB]
}

Order of run is different with:

{
 "workspaces": \[lB] "packages/b", "packages/a" \[rB]
}

It is not required for all of the workspaces to implement scripts run with the npm run command.

By running the command with the --if-present flag, npm will ignore workspaces missing target script.

npm run test --workspaces --if-present