package.json scripts

Learn to define commands with package.json scripts.

package.json scripts

The scripts section is where you define frequently used commands with short names. When you write "scripts": { "dev": "nodemon server.js" } in package.json, you run that command with npm run dev.

Two scripts are special: start and test. They run with npm start and npm test; the word run is not needed. All other scripts are called as npm run <name>, for example npm run build or npm run lint. This way you run long commands through short names, and your teammates use the same commands.

Built-in scripts

start and test are npm's built-in scripts. They run directly with npm start and npm test; no run is needed.

For example, if you define "scripts": { "start": "node server.js", "test": "jest" }, then npm start launches the server and npm test runs the tests. Other scripts (dev, build, lint) require npm run <name>. This distinction provides a shortcut for the two most common commands. You can also define scripts that run before or after another script using the pre and post prefixes; for example pretest runs before the tests.

Exercise Print the start script value

Define a string named content with the value {"name":"my-app","scripts":{"start":"node server.js","dev":"nodemon server.js"}}. Parse it into an object with JSON.parse. Print pkg.scripts.start with console.log.

Show example solution

const content = '{"name":"my-app","scripts":{"start":"node server.js","dev":"nodemon server.js"}}';
const pkg = JSON.parse(content);
console.log(pkg.scripts.start);

Test yourself

Complete the run command
```
npm ____ dev
```
Show answer
```
npm run dev
```
Match each command to its trigger

npm start

Runs the start script
npm test

Runs the test script
npm run dev

Runs the dev script
npm run build

Runs the build script
Which command runs a custom 'dev' script?
```
npm run dev
```
- npm dev
- npm start dev
- npm run dev
- npm run start
Show answer

npm run dev — Custom scripts run with npm run <name>.

Next lesson: devDependencies

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