TypeScript Project Setup

The following steps set up a bare bones TypeScript project that is suitable for writing code in TypeScript and testing code using Jest.

mkdir -p my-test-project/src
cd my-test-project

npm init --yes
npm i -D @types/jest @types/node jest prettier ts-jest typescript
npx tsc --init
npx ts-jest config:initCode language: Shell Session (shell)

That should set you up with:

ls -bp1

jest.config.js
node_modules/
package.json
package-lock.json
src/
tsconfig.json

I would also then edit package.json as follows:

  "scripts": {
    "start:tsc": "tsc -w",
    "test": "jest",
    "test:watch": "jest --watchAll --runInBand --coverage"
  },Code language: JSON / JSON with Comments (json)

This will allow me to run:

• npm run test:watch
  from the command line and get Jest to run as I code
• npm run start:tsc
  from the command line and make TypeScript compile the source code to JS in real time / on save

One other change I make, which is not mandatory but one that I personally like is to set TypeScript to build code to a different directory than the source TS files:

// tsconfig.json

{
  "compilerOptions": {
    "target": "es2016",
    "module": "commonjs",
    "outDir": "./dist",
    "esModuleInterop": true,
    "forceConsistentCasingInFileNames": true,
    "strict": true,
    "skipLibCheck": true
  },
  "exclude": [
    "node_modules",
    "**/*.spec.ts"
  ]
}Code language: JSON / JSON with Comments (json)

Assuming you then create a file at src/index.ts, the compiler will spit out a dist/index.js file, and so on.

If you go with this approach, ensure you exclude the outDir path from the list of directories that Jest will look in to find your tests:

// jest.config.js

/** @type {import('ts-jest').JestConfigWithTsJest} */
module.exports = {
  preset: "ts-jest",
  testEnvironment: "node",
  testPathIgnorePatterns: ["./dist"],
};Code language: JavaScript (javascript)