Extending the Form Engine

You might want to customize the Form Engine in various ways. For example, you might want to:

• Add custom expression helpers.
• Add custom validators and error logic.
• Add custom components.
• Add custom fields.
• Add custom styling.
• Change how expressions get run.
• Change how questions, sections and pages get rendered, and so on.

Running the Form Engine locally

• Fork and clone the Form Engine (opens in a new tab) repository.

• Install dependencies by running:

  yarn install --immutable

• Launch a live development server on port 4200 using:

  yarn start

  Visit http://localhost:4200 in your browser. You should see the sample form (opens in a new tab) rendered by the demo app in src/app. Here, you're able to interact with the various form fields and even submit the form.

• Modify the Form Engine. Changes made to the Form Engine will be reflected automatically in the live development server.

• To build the distributable library, run:

  yarn build:lib

See the repository README (opens in a new tab) for prerequisites, testing commands, and how to link a local build into an O3 frontend.