Introduction to npm-run-script

npm-run-script is a powerful feature of npm that allows developers to run custom scripts defined in the package.json file. This enables a wide range of automation possibilities in Node.js-based projects. In this guide, we will explore various APIs of npm-run-script with practical code snippets and provide an example application to demonstrate its usage.

Basic Usage

To define a script in the package.json file, add a “scripts” section with the desired command:

  {
    "scripts": {
      "start": "node app.js",
      "test": "mocha"
    }
  }

With these definitions, you can run the scripts using npm:

  npm start
  npm test

Dozens of Useful APIs

Here are some useful npm-run-script APIs with examples:

Pre and Post Hooks

You can define pre and post hooks for any script:

  {
    "scripts": {
      "prestart": "echo 'Preparing to start...'",
      "start": "node app.js",
      "poststart": "echo 'Server has started.'"
    }
  }

Running Multiple Scripts

Use the ‘&&’ operator to run multiple scripts sequentially:

  {
    "scripts": {
      "lint": "eslint .",
      "test": "mocha",
      "ci": "npm run lint && npm run test"
    }
  }

Environment Variables

Set environment variables within scripts:

  {
    "scripts": {
      "start": "NODE_ENV=production node app.js"
    }
  }

Using npm-run-all

Install npm-run-all to run scripts concurrently or sequentially:

  npm install npm-run-all --save-dev

Then define scripts to use npm-run-all:

  {
    "scripts": {
      "clean": "rimraf dist",
      "build": "webpack",
      "start": "node server.js",
      "dev": "npm-run-all clean build start"
    }
  }

Example Application

Let’s create a small application to demonstrate the usage of npm-run-script APIs. We will set up a Node.js server with scripts for cleaning, building, and starting the server.

  {
    "name": "example-app",
    "version": "1.0.0",
    "scripts": {
      "clean": "rimraf dist",
      "build": "webpack",
      "start": "node server.js",
      "dev": "npm-run-all clean build start"
    },
    "devDependencies": {
      "rimraf": "^3.0.2",
      "webpack": "^5.36.2",
      "npm-run-all": "^4.1.5"
    }
  }

Here’s a basic server.js file:

   const express = require('express');
   const app = express();
   const PORT = process.env.PORT || 3000;
   
   app.get('/', (req, res) => {
     res.send('Hello World');
   });
   
   app.listen(PORT, () => {
     console.log(`Server is running on port ${PORT}`);
   });

With this setup, you can easily manage your development workflow with npm-run-script. Run the whole development setup with a single command:

  npm run dev

Enjoy automating your Node.js project’s tasks efficiently!

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