Hello world

A Probot app is just a Node.js module that exports a function:

export default (app) => {
  // your code here
};

The app parameter is an instance of Probot and gives you access to all of the GitHub goodness.

app.on will listen for any webhook events triggered by GitHub, which will notify you when anything interesting happens on GitHub that your app wants to know about.

export default (app) => {
  app.on("issues.opened", async (context) => {
    // A new issue was opened, what should we do with it?
    context.log.info(context.payload);
  });
};

The context passed to the event handler includes everything about the event that was triggered, as well as some helpful properties for doing something useful in response to the event. context.octokit is an authenticated GitHub client that can be used to make REST API and GraphQL calls, and allows you to do almost anything programmatically that you can do through a web browser on GitHub.

Here is an example of an autoresponder app that comments on opened issues:

export default (app) => {
  app.on("issues.opened", async (context) => {
    // `context` extracts information from the event, which can be passed to
    // GitHub API calls. This will return:
    //   { owner: 'yourname', repo: 'yourrepo', number: 123, body: 'Hello World !}
    const params = context.issue({ body: "Hello World!" });

    // Post a comment on the issue
    return context.octokit.issues.createComment(params);
  });
};