codex-lv3-may-2025

Level Navigation: 1

Level 3: Set up the project

First, initialize your npm project and install Vitest:

npm init -y
npm install --save-dev vitest

Then, update your package.json to add the test script and set the module type:

{
  "type": "module",
  "scripts": {
    "test": "vitest"
  }
}

Show Me: What the full package.json might look like

When you run npm init -y, it creates a basic package.json (see [npm](/codex-lv3-may-2025/VOCABULARY_LIST.html#npm) for more on npm commands). After adding the type and scripts fields, your complete package.json might look like this:


{
  "name": "function-practice",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "type": "module",
  "scripts": {
    "test": "vitest"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "vitest": "^1.0.0"
  }
}

Key points:

The "type": "module" field enables ES6 module syntax (import/export)
The "scripts" section includes your test command
vitest appears in devDependencies after installation
Other fields (name, version, etc.) are created by npm init -y

Now run the test command to verify Vitest is set up correctly (it will show no tests found, which is expected):

npm run test

🔍 Diving Deeper

devDependencies live in your package.json so tooling like Vitest is only installed for development, keeping production bundles lean.
Setting "type": "module" unlocks ES module syntax. See the type: “module” entry for a refresher on why modern bundlers like Vite expect ESM by default.
npm run test executes the script you defined. Review npm scripts to see how custom commands plug into your workflow.

Press q to quit the test runner when you’re done checking.

codex-lv3-may-2025

Level 3: Set up the project

🔍 Diving Deeper

Key Terms