How to install typescript + jest with create-react-app?

Question

I want to install typescript and jest in a create-react-app-based app. I feel that since this is such a common installation choice there must be at least one "everything just works" set of configuration steps to follow.

I initially ran npx create-react-app my-project --template typescript. That was great for a while. I wrote several thousand lines of code with that. And then one day I decided I wanted to add some mocks to a spec file with code like this:

import jest from "jest";

jest.mock('./somemodule');

...but the "jest" instance is undefined. So I followed directions in different articles to install further devDependencies. But these seem to conflict with dependencies inside of create-react-app, suggesting that I need to focus on setting up my project correctly the "Create-react-app Way" according to its expectations.

Rather than burden StackOverflow with the details of my build and package management issues, I figure I'll just ask the simpler question - what is the correct way to set up create-react-app+typescript+jest in a way where it doesn't have a bunch of irritating, random problems?

And then after I've followed this advice, if I still have problems, I might ask a second, separate SO question with specific details.

Answer 1

The command below should create a new React project supporting Typescript and Jest without need of further modification.

npx create-react-app my-app --template typescript

Details about the above command can be found here: https://create-react-app.dev/docs/adding-typescript/

The above command will set up a new project. But if, like me, you have an existing create-react-app project with issues like:

• the Jest module is undefined or doesn't seem to have expected functions
• your npm run start and npm run build fail due to conflicting dependencies
• or you just want to get to a "standard" package.json configuration without all the hassle of copying your source into a new project.

...you can use the process below to fix/upgrade your package.json:

1. Use the same npx create-react-app my-app --template typescript command above to create a separate working ("Good") project with all the right dependencies. This project will just be used as a reference.
2. Compare the package.json of the Good project to the non-working ("Bad") project, and make sure the Bad package.json has the same modules and version#s as the Good package.json. You probably don't have to delete any modules in the Bad package.json that aren't in the Good package.json.
3. rm -rf node-modules in the Bad project.
4. rm package-lock.json in the Bad project.
5. npm install in the Bad project.

Self-answering for posterity.