Nx and TypeScript

The build system for TypeScript that TypeScript deserves

The @nrwl/js package ships with corresponding generators and executors that best work when it comes to developing TypeScript applications and libraries.

Note, you can also opt-out of TypeScript and use plain JavaScript by passing the --js flag to the generators.

@nrwl/js is particularly useful if you want to

  • Create framework agnostic TypeScript libraries within an existing Nx workspace (say to use in your React, Node or Angular app)
  • Publish TypeScript packages to NPM

To get started with TypeScript packages in Nx, either add the @nrwl/js package to an existing Nx workspace or generate a new Nx workspace using the --preset=ts preset.

npx create-nx-workspace happynrwl -–preset=ts

Generating a new workspace creates a lightweight setup with a packages and tools folder. The tools folder is where you can add monorepo specific scripts and custom Nx generators, the packages folder is where all our TS based libs will live.

├── packages/
├── tools/
├── workspace.json
├── nx.json
├── package.json
└── tsconfig.base.json

As with most Nx plugins, @nrwl/js comes with a set of generators to quickly scaffold new TypeScript libraries as well as TypeScript applications. Let’s have a look at an example.

Create a new TypeScript based library

We can use Nx Console and choose the @nrwl/js:library generator or directly use the following command:

nx generate @nrwl/js:library --name=hello-tsc --buildable

This creates a new library in the packages/hello-tsc folder that already comes with both ESLint and Jest set up and ready to use.

You can run nx lint hello-tsc to run linting or nx test hello-tsc to run Jest tests.

Note, by passing the --buildable flag, our library can be built.

nx build hello-tsc

The output of the build step is placed into the dist/packages/hello-tsc by default.

Create a TypeScript based application

Apart from setting up TypeScript libraries, you can also setup a plain TypeScript application that is framework agnostic and consists of an entry point script that can be easily run with Node, to develop a CLI or framework agnostic backend application.

To generate a new framework agnostic TS application, run

nx generate @nrwl/js:app demoapp

Applications also come with a “serve” target, that allow you to run the app in watch mode:

nx serve demoapp

Importing Libraries

All the libraries generated within the Nx workspace are configured with corresponding TypeScript path mappings in the root-level tsconfig.base.json file:

2  "compileOnSave": false,
3  "compilerOptions": {
4    ...
5    "paths": {
6      "@happynrwl/hello-swc": ["packages/hello-swc/src/index.ts"],
7      "@happynrwl/hello-tsc": ["packages/hello-tsc/src/index.ts"]
8    }
9  },

This allows you to easily import from libraries, by using the corresponding TypeScript path mapping. The following shows an example of importing the helloTsc function from the hello-tsc library into the tsapp application (the same method works between libraries as well):

1// file: packages/tsapp/src/index.ts
3// importing from hello-tsc
4import { helloTsc } from '@happynrwl/hello-tsc';
6// use the function
9console.log(`Running ${tsapp()}`);

Use SWC as the compiler

Nx also ships with support to use SWC instead of TSC. When generating a new library/application just pass the --compiler=swc.

Here's an example of generating a new library:

nx generate @nrwl/js:library --name=hello-tsc --buildable --compiler=swc

Alternatively, if you already have an existing tsc based library/application, you can run the @nrwl/js:convert-to-swc generator to migrate the package from TSC to SWC.

The following command converts the hello-tsc library to SWC:

nx generate @nrwl/js:convert-to-swc --name=hello-tsc

Using NPM Scripts rather than Nx executors

If you want to use NPM scripts rather than Nx executors, you can use the --config=npm-scripts:

nx g @nrwl/js:lib mylib --config=npm-scripts

The Nx generator then creates NPM scripts in the generated library's package.json (rather than in the project.json):

1// packages/mylib/package.json
3  "name": "@happynrwl/mylib",
4  "version": "0.0.1",
5  "type": "commonjs",
6  "scripts": {
7    "build": "echo 'implement build'",
8    "test": "echo 'implement test'"
9  }

To run these scripts with Nx, use the same syntax as Nx executors. nx build mylib or nx test mylib will build or test your library, respectively.

Publish your TypeScript packages to NPM

Nx doesn’t provide an out of the box process for publishing and leaves it to the developer to invoke the final command. The reason for this is that the actual publishing process can be very specific to your project and target you deploy to and might have a lot of custom pre-deployment setup (e.g. generating changelogs, determining semver etc.). Make sure to check out our community page as there are a lot of community provided packages integrating into the publishing process.

However, integrating your own custom publishing process with Nx can be very straightforward, especially with the help of Nx run-commands and “Target Dependencies”.

To add a new run-command to our project, we can leverage the run-command generator:

nx g @nrwl/workspace:run-commands publish --project hello-tsc --command 'npm publish --tag=latest --access public'

This adds a new publish target to our existing project.json configuration of the hello-tsc project. Let's also make sure to adjust the cwd (current working directory) of our command, which should be the output folder of the hello-tsc package.

2  "root": "packages/hello-tsc",
3  "sourceRoot": "packages/hello-tsc/src",
4  "projectType": "library",
5  "targets": {
6    "build": { ... },
7    "lint": { ... },
8    "test": { ... },
9    "publish": {
10      "executor": "@nrwl/workspace:run-commands",
11      "outputs": [],
12      "options": {
13        "command": "npm publish --tag=latest --access public",
14        "cwd": "dist/packages/hello-tsc"
15      }
16    }
17  },
18  "tags": []

With that, we're all set up. By running the following commands we can publish our package to NPM.

nx build hello-tsc
nx publish hello-tsc

We can automate this even further by leveraging the targetDependencies feature. There's clearly a dependency between build and publish, in that we want to make sure the build happens before the publish command. We can define this relationship in the nx.json file:

2  ...
3  "targetDependencies": {
4    ...
5    "publish": [
6      {
7        "target": "build",
8        "projects": "self"
9      }
10    ]
11  },
12  ...

Now, just running nx publish hello-tsc will automatically run the nx build hello-tsc command first. And of course, if build has already run, it won't execute again, thanks to Nx computation caching.