Run Tasks

Monorepos can have hundreds or even thousands of projects, so being able to run actions against all (or some) of them is a key feature of a tool like Nx.

Definitions

  • Command - anything the developer types into the terminal (e.g., nx run header:build).
  • Target - the name of an action taken on a project (e.g., build)
  • Task - an invocation of a target on a specific project (e.g., header:build).

Define Tasks

For these examples, we'll imagine a repo that has three projects: myapp, header and footer. myapp is a deployable app and uses the header and footer libraries.

Each project has the test and build targets defined. Tasks can be defined as npm scripts in a project's package.json file or as targets in a project.json file:

package.json
1{ 2 "scripts": { 3 "build": "webpack -c webpack.conf.js", 4 "test": "jest --coverage" 5 } 6} 7

Running Tasks

Nx uses the following syntax:

Syntax for Running Tasks in Nx

Run a Single Task

To run the test target on the header project run this command:

❯

npx nx test header

Run Tasks for Multiple Projects

You can use the run-many command to run a task for multiple projects. Here are a couple of examples.

Run the build target for all projects in the repo:

❯

npx nx run-many -t build

Run the build, lint and test target for all projects in the repo:

❯

npx nx run-many -t build lint test

Run the build, lint and test target just on the header and footer projects:

❯

npx nx run-many -t build lint test -p header footer

Note that Nx parallelizes all these tasks making also sure they are run in the right order based on their dependencies and the task pipeline configuration.

Learn more about the run-many command.

Run Tasks in Parallel

If you want to increase the number of processes running tasks to, say, 5 (by default, it is 3), pass the following:

❯

npx nx build myapp --parallel=5

Note, you can also change the default in nx.json, like this:

nx.json
1{ 2 "parallel": 5 3} 4

Run Tasks on Projects Affected by a PR

You can also run a command for all the projects affected by your PR like this:

❯

npx nx affected -t test

Learn more about the affected command here.

Defining a Task Pipeline

It is pretty common to have dependencies between tasks, requiring one task to be run before another. For example, you might want to run the build target on the header project before running the build target on the app project.

Nx is already able to automatically understand the dependencies between projects (see project graph).

However, you need to define for which targets such ordering matters. In the following example we are telling Nx that before running the build target it needs to run the build target on all the projects the current project depends on:

nx.json
1{ 2 ... 3 "targetDefaults": { 4 "build": { 5 "dependsOn": ["^build"] 6 } 7 } 8} 9

Meaning, if we run nx build myreactapp, Nx will first run build on modules-shared-ui and modules-products before running build on myreactapp. You can define these task dependencies globally for your workspace in nx.json or individually in each project's project.json file.

Learn all the details:

Run Root-Level Tasks

Sometimes you have tasks that apply to the entire codebase rather than to a single project. But you still want those tasks to go through the "Nx pipeline" in order to benefit from caching. You can define these in the root-level package.json as follows:

package.json
1{ 2 "name": "myorg", 3 "scripts": { 4 "docs": "node ./generateDocsSite.js" 5 }, 6 "nx": {} 7} 8

Note the nx: {} property on the package.json. This is necessary to inform Nx about this root-level project. The property can also be expanded to specify cache inputs and outputs.

To invoke it, use:

❯

npx nx docs

If you want Nx to cache the task, but prefer to use npm (or pnpm/yarn) to run the script (i.e. npm run docs) you can use the nx exec command:

package.json
1{ 2 "name": "myorg", 3 "scripts": { 4 "docs": "nx exec -- node ./generateDocsSite.js" 5 }, 6 "nx": {} 7} 8

Learn more about root-level tasks in our dedicated recipe page.