OK, you fall in love with typescript, and now you really want to use it in your new express project.

A common approach in using typescript in node project

Start the new node project by running this command in your directory via the terminal.

1. Create a new node project, with a package.json file

npm init

This will generate a new package.json file. Let me show mine:

{
  "name": "friend-api",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "Teerasej Jiraphatchandej",
  "license": "ISC"
}

2. Add packages for typescript

So we want to set up this project for us to use typescript in development. We add 2 packages as devDependencies:

npm i -D @types/node
npm i -D typescript

Here we go. We have package.json file similar to the one below:

{
  "name": "friend-api",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "Teerasej Jiraphatchandej",
  "license": "ISC",
  "devDependencies": {
    "@types/node": "^17.0.29",
    "typescript": "^4.6.3"
  },
}

3. Add tsconfig.json

OK, let's create another file: tsconfig.json at the root of the project's directory. This file will tell how would typescript's compiler work:

{
    "compilerOptions": {
      "module": "commonjs",
      "esModuleInterop": true,
      "target": "es6",
      "moduleResolution": "node",
      "sourceMap": true,
      "outDir": "dist"
    },
    "lib": ["es2015"]
}

5. Let compile and run

from this point, you can use the following command in the terminal to compile all tsc files in project into /dist directory (as you set it up in tsconfig.json: outDir)

tsc

and you can run your compiled code with

node dist/<file name>.js

6. Done, but you can add more ease

Execute 2 commands repeatedly will take out our energy. You can use the script section in package.json to create a shortcut

{
  ...
  "scripts": {
    "start": "tsc && node dist/app.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  ...
}

After save the package.json file, you can compile and run your project with one simple command:

npm run start