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Creating a JavaScript action |
Create a JavaScript action |
In this guide, you'll learn how to build a JavaScript action using the actions toolkit. |
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tutorial |
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{% data reusables.actions.enterprise-github-hosted-runners %}
In this guide, you'll learn about the basic components needed to create and use a packaged JavaScript action. To focus this guide on the components needed to package the action, the functionality of the action's code is minimal. The action prints "Hello World" in the logs or "Hello [who-to-greet]" if you provide a custom name.
This guide uses the {% data variables.product.prodname_actions %} Toolkit Node.js module to speed up development. For more information, see the actions/toolkit repository.
Once you complete this project, you should understand how to build your own JavaScript action and test it in a workflow.
{% data reusables.actions.pure-javascript %}
{% data reusables.actions.context-injection-warning %}
Before you begin, you'll need to download Node.js and create a public {% data variables.product.prodname_dotcom %} repository.
-
Download and install Node.js 20.x, which includes npm.
https://nodejs.org/en/download/
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Create a new public repository on {% data variables.product.github %} and call it "hello-world-javascript-action". For more information, see AUTOTITLE.
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Clone your repository to your computer. For more information, see AUTOTITLE.
-
From your terminal, change directories into your new repository.
cd hello-world-javascript-action -
From your terminal, initialize the directory with npm to generate a
package.jsonfile.npm init -y
Create a new file named action.yml in the hello-world-javascript-action directory with the following example code. For more information, see AUTOTITLE.
name: 'Hello World'
description: 'Greet someone and record the time'
inputs:
who-to-greet: # id of input
description: 'Who to greet'
required: true
default: 'World'
outputs:
time: # id of output
description: 'The time we greeted you'
runs:
using: 'node20'
main: 'index.js'This file defines the who-to-greet input and time output. It also tells the action runner how to start running this JavaScript action.
The actions toolkit is a collection of Node.js packages that allow you to quickly build JavaScript actions with more consistency.
The toolkit @actions/core package provides an interface to the workflow commands, input and output variables, exit statuses, and debug messages.
The toolkit also offers a @actions/github package that returns an authenticated Octokit REST client and access to GitHub Actions contexts.
The toolkit offers more than the core and github packages. For more information, see the actions/toolkit repository.
At your terminal, install the actions toolkit core and github packages.
npm install @actions/core
npm install @actions/githubNow you should see a node_modules directory with the modules you just installed and a package-lock.json file with the installed module dependencies and the versions of each installed module.
This action uses the toolkit to get the who-to-greet input variable required in the action's metadata file and prints "Hello [who-to-greet]" in a debug message in the log. Next, the script gets the current time and sets it as an output variable that actions running later in a job can use.
GitHub Actions provide context information about the webhook event, Git refs, workflow, action, and the person who triggered the workflow. To access the context information, you can use the github package. The action you'll write will print the webhook event payload to the log.
Add a new file called index.js, with the following code.
{% raw %}
const core = require('@actions/core');
const github = require('@actions/github');
try {
// `who-to-greet` input defined in action metadata file
const nameToGreet = core.getInput('who-to-greet');
console.log(`Hello ${nameToGreet}!`);
const time = (new Date()).toTimeString();
core.setOutput("time", time);
// Get the JSON webhook payload for the event that triggered the workflow
const payload = JSON.stringify(github.context.payload, undefined, 2)
console.log(`The event payload: ${payload}`);
} catch (error) {
core.setFailed(error.message);
}{% endraw %}
If an error is thrown in the above index.js example, core.setFailed(error.message); uses the actions toolkit @actions/core package to log a message and set a failing exit code. For more information, see AUTOTITLE.
To let people know how to use your action, you can create a README file. A README is most helpful when you plan to share your action publicly, but is also a great way to remind you or your team how to use the action.
In your hello-world-javascript-action directory, create a README.md file that specifies the following information:
- A detailed description of what the action does.
- Required input and output arguments.
- Optional input and output arguments.
- Secrets the action uses.
- Environment variables the action uses.
- An example of how to use your action in a workflow.
# Hello world javascript action
This action prints "Hello World" or "Hello" + the name of a person to greet to the log.
## Inputs
### `who-to-greet`
**Required** The name of the person to greet. Default `"World"`.
## Outputs
### `time`
The time we greeted you.
## Example usage
```yaml
uses: actions/hello-world-javascript-action@e76147da8e5c81eaf017dede5645551d4b94427b
with:
who-to-greet: 'Mona the Octocat'
```{% data variables.product.github %} downloads each action run in a workflow during runtime and executes it as a complete package of code before you can use workflow commands like run to interact with the runner machine. This means you must include any package dependencies required to run the JavaScript code. You'll need to check in the toolkit core and github packages to your action's repository.
From your terminal, commit your action.yml, index.js, node_modules, package.json, package-lock.json, and README.md files. If you added a .gitignore file that lists node_modules, you'll need to remove that line to commit the node_modules directory.
It's best practice to also add a version tag for releases of your action. For more information on versioning your action, see AUTOTITLE.
git add action.yml index.js node_modules/* package.json package-lock.json README.md
git commit -m "My first action is ready"
git tag -a -m "My first action release" v1.1
git push --follow-tagsChecking in your node_modules directory can cause problems. As an alternative, you can use a tool called @vercel/ncc to compile your code and modules into one file used for distribution.
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Install
vercel/nccby running this command in your terminal.npm i -g @vercel/ncc -
Compile your
index.jsfile.ncc build index.js --license licenses.txtYou'll see a new
dist/index.jsfile with your code and the compiled modules. You will also see an accompanyingdist/licenses.txtfile containing all the licenses of thenode_modulesyou are using. -
Change the
mainkeyword in youraction.ymlfile to use the newdist/index.jsfile.main: 'dist/index.js' -
If you already checked in your
node_modulesdirectory, remove it.rm -rf node_modules/* -
From your terminal, commit the updates to your
action.yml,dist/index.js, andnode_modulesfiles.git add action.yml dist/index.js node_modules/* git commit -m "Use vercel/ncc" git tag -a -m "My first action release" v1.1 git push --follow-tags
Now you're ready to test your action out in a workflow.
Public actions can be used by workflows in any repository. When an action is in a private{% ifversion ghec or ghes %} or internal{% endif %} repository, the repository settings dictate whether the action is available only within the same repository or also to other repositories owned by the same {% ifversion ghec or ghes %}organization or enterprise{% else %}user or organization{% endif %}. For more information, see AUTOTITLE.
{% data reusables.actions.enterprise-marketplace-actions %}
This example demonstrates how your new public action can be run from within an external repository.
Copy the following YAML into a new file at .github/workflows/main.yml, and update the uses: octocat/hello-world-javascript-action@1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b line with your username and the name of the public repository you created above. You can also replace the who-to-greet input with your name.
{% raw %}
on: [push]
jobs:
hello_world_job:
runs-on: ubuntu-latest
name: A job to say hello
steps:
- name: Hello world action step
id: hello
uses: octocat/hello-world-javascript-action@1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b
with:
who-to-greet: 'Mona the Octocat'
# Use the output from the `hello` step
- name: Get the output time
run: echo "The time was ${{ steps.hello.outputs.time }}"{% endraw %}
When this workflow is triggered, the runner will download the hello-world-javascript-action action from your public repository and then execute it.
Copy the workflow code into a .github/workflows/main.yml file in your action's repository. You can also replace the who-to-greet input with your name.
.github/workflows/main.yml
on: [push]
jobs:
hello_world_job:
runs-on: ubuntu-latest
name: A job to say hello
steps:
# To use this repository's private action,
# you must check out the repository
- name: Checkout
uses: {% data reusables.actions.action-checkout %}
- name: Hello world action step
uses: ./ # Uses an action in the root directory
id: hello
with:
who-to-greet: 'Mona the Octocat'
# Use the output from the `hello` step
- name: Get the output time
run: echo "The time was {% raw %}${{ steps.hello.outputs.time }}{% endraw %}"{% data reusables.actions.test-private-action-example %}
{% data variables.product.prodname_dotcom %} provides template repositories for creating JavaScript and TypeScript actions. You can use these templates to quickly get started with creating a new action that includes tests, linting, and other recommended practices.
You can find many examples of JavaScript actions on {% data variables.product.prodname_dotcom_the_website %}.