Package Management

// package.json
{
    "name": "my-project",
    "version": "1.0.0",
    "description": "A sample project",
    "main": "index.js",
    "scripts": {
        "start": "node index.js",
        "dev": "nodemon index.js",
        "build": "webpack --mode production",
        "test": "jest",
        "lint": "eslint src/"
    },
    "dependencies": {
        "express": "^4.18.0",
        "lodash": "^4.17.21"
    },
    "devDependencies": {
        "jest": "^29.0.0",
        "eslint": "^8.0.0"
    }
}

// Installing packages
npm install express          // Production dependency
npm install -D jest          // Development dependency
npm install -g nodemon       // Global package

// Version management
npm install express@4.17.1   // Specific version
npm install express@^4.17.0  // Compatible version
npm install express@~4.17.1  // Patch version

// Updating packages
npm update                   // Update all packages
npm update express           // Update specific package
npm outdated                 // Check outdated packages

// Yarn commands
yarn add express             // Add dependency
yarn add -D jest             // Add dev dependency
yarn install                 // Install dependencies
yarn upgrade                 // Update dependencies

// pnpm commands
pnpm add express             // Add dependency
pnpm add -D jest             // Add dev dependency
pnpm install                 // Install dependencies
pnpm update                  // Update dependencies

// Performance comparison
// pnpm > yarn > npm (in terms of speed and disk usage)

// Monorepo with workspaces
// package.json (root)
{
    "name": "my-monorepo",
    "workspaces": [
        "packages/*",
        "apps/*"
    ]
}

// packages/shared/package.json
{
    "name": "@myorg/shared",
    "version": "1.0.0"
}

// apps/web/package.json
{
    "name": "@myorg/web",
    "dependencies": {
        "@myorg/shared": "workspace:*"
    }
}

// Simple package manager
const fs = require('fs');
const path = require('path');

class SimplePackageManager {
    constructor(projectPath) {
        this.projectPath = projectPath;
        this.packageJsonPath = path.join(projectPath, 'package.json');
        this.nodeModulesPath = path.join(projectPath, 'node_modules');
        this.packageJson = this.loadPackageJson();
    }

    loadPackageJson() {
        if (fs.existsSync(this.packageJsonPath)) {
            return JSON.parse(fs.readFileSync(this.packageJsonPath, 'utf8'));
        }
        return {
            name: path.basename(this.projectPath),
            version: '1.0.0',
            dependencies: {},
            devDependencies: {}
        };
    }

    addDependency(name, version, isDev = false) {
        const key = isDev ? 'devDependencies' : 'dependencies';
        this.packageJson[key][name] = version;
        this.savePackageJson();
        console.log(`Added ${name}@${version} to ${key}`);
    }

    removeDependency(name) {
        let removed = false;
        if (this.packageJson.dependencies[name]) {
            delete this.packageJson.dependencies[name];
            removed = true;
        }
        if (this.packageJson.devDependencies[name]) {
            delete this.packageJson.devDependencies[name];
            removed = true;
        }

        if (removed) {
            this.savePackageJson();
            console.log(`Removed ${name}`);
        } else {
            console.log(`Package ${name} not found`);
        }
    }

    listDependencies() {
        console.log('Dependencies:');
        Object.entries(this.packageJson.dependencies).forEach(([name, version]) => {
            console.log(`  ${name}: ${version}`);
        });

        console.log('Dev Dependencies:');
        Object.entries(this.packageJson.devDependencies).forEach(([name, version]) => {
            console.log(`  ${name}: ${version}`);
        });
    }

    savePackageJson() {
        fs.writeFileSync(
            this.packageJsonPath,
            JSON.stringify(this.packageJson, null, 2)
        );
    }
}