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* refactor: move polyfills used in main JS thread into a single file

* doc: add explanations for each

* feat(performance): only IE11 should receive existing polyfills

* docs(browser-detection): add reminder that isInternetExplorer() is not safe to call from a WebWorker context

* refactor(worker): only polyfill if Promise is unavailable.

* fix: avoid transpiling polyfills since they pneed to monkey patch native APIs

* fix(regenerator-runtime): babel transpilation expects library to be available in global namespace

* refactor(ndjson-stream): remove polyfills and document code better

* fix: remove misleading comments

* refactor: convert from browser detection to feature detection

Co-authored-by: Yuanruo Liang <>

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Aug 3, 2020


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Table of Contents


FormSG is a form builder application built, open sourced and maintained by the Open Government Products team of the Singapore Government Technology Agency to digitise paper processes.

Notable features include:

  • 19 different form field types, including attachments, tables, email and mobile
  • Verified email and mobile phone fields via integrations with Twilio and AWS SES
  • Automatic emailing of submissions for forms built with Email Mode
  • End-to-end encryption for forms built with Storage Mode
  • (Singapore government agencies only) Citizen authentication with SingPass
  • (Singapore government agencies only) Corporate authentication with CorpPass
  • (Singapore government agencies only) Automatic prefill of verified data with MyInfo
  • (beta) Webhooks functionality via the FormSG JavaScript SDK.

The current product roadmap includes:

  • (in progress) Migrating backend code from JavaScript to TypeScript
  • (in progress) Refactoring backend code to use Domain-driven Design
  • (in progress) Migrating backend tests from Jasmine to Jest and expanding unit vs integration tests
  • (yet to start) Support for webhooks attachments
  • (yet to start) Frontend rewrite from AngularJS to React

Local Development (Docker)


Install docker and docker-compose.

Running Locally

Run the following shell command to build the Docker image from scratch. This will usually take 10 or so minutes.

npm run dev

After the Docker image has finished building, the application can be accessed at localhost:5000.

If there have been no dependency changes in package.json or changes in the src/server.ts file, you can run

docker-compose up

which does not rebuild the Docker image from scratch. This command usually only takes ~15 seconds to finish starting up the image.

Accessing email locally

We use MailDev to access emails in the development environment. The MailDev UI can be accessed at localhost:1080 when the Docker container is running.

Environment variables

Docker-compose looks at various places for environment variables to inject into the containers. The following is the order of priority:

  • Compose file
  • Shell environment variables
  • Environment file
  • Dockerfile

FormSG requires some environment variables in order to function. More information about the required environment variables can be seen in

The docker-compose file declares some blank environment variables that are secret and cannot be committed into the repository. See below instructions to get them injected into the container.

We provide a .template-env file with the secrets blanked out. You can copy and paste the variables described into a self-created .env file, replacing the required values with your own.


You can consult for common issues that developers face and how to resolve them.


The docker environment has not been configured to run tests. Thus, you will need to follow the following local build guide to get tests running locally.

Testing Prerequisites

The team uses macOS for development.

Make you sure have the following node version & package manager on your machine:

  • "node": ">=12.18.0"
  • "npm": ">=6.0.0"
  • "mongo": ">=3.6.0"


nvm install 12.18.0
npm install
pip install "localstack[full]"

to install node modules and Localstack locally to be able to run tests. Note that localstack[full] is only compatible with Python 3.7 and above.

Running tests

Unit tests

npm run test

will build the backend and run both our backend and frontend unit tests. The tests are located at tests/unit/frontend and tests/unit/backend.

If the backend is already built, you can run

npm run test-ci

End-to-end tests

npm run test-e2e

will build both the frontend and backend then run our end-to-end tests. The tests are located at tests/end-to-end. You will need to stop the Docker dev container to be able to run the end-to-end tests.

If you do not need to rebuild the frontend and backend, you can run

npm run test-e2e-ci


An overview of the architecture can be found here.

MongoDB Scripts

Scripts for common tasks in MongoDB can be found here.

Maintenance Banners

Banners providing form-fillers with useful information can shown at the top of forms and configured using the environment variables below.

Environment Variable Value will be shown as a banner at the bottom of
ADMIN_BANNER_CONTENT private form routes such as /forms and /{formId}/admin
SITE_BANNER_CONTENT both private routes that ADMIN_BANNER_CONTENT covers and public form routes that IS_GENERAL_MAINTENANCE covers. This supersedes ALL other banner environment variables
IS_SP_MAINTENANCE all public SingPass-enabled forms
IS_CP_MAINTENANCE all public CorpPass-enabled forms

Note that if more than one of the above environment variables are defined, only one environment variable will be used to display the given values.

For public form routes, only one environment variable will be read in the following precedence: SITE_BANNER_CONTENT > IS_GENERAL_MAINTENANCE > IS_SP_MAINTENANCE > IS_CP_MAINTENANCE

For private form routes, only one environment variable will be read in the following precendence: SITE_BANNER_CONTENT > ADMIN_BANNER_CONTENT


We welcome all contributions, bug reports, bug fixes, documentation improvements, enhancements, and ideas to code open sourced by the Government Technology Agency of Singapore. Contributors should read and will also be asked to sign a Contributor License Agreement (CLA) in order to ensure that everybody is free to use their contributions.


Please contact FormSG ( for any details.


FormSG acknowledges the work done by Arielle Baldwynn to build and maintain TellForm, on which FormSG is based.

Contributions have also been made by: