Set an environment variable inline when running Node.js
📦 Node.js-> Command Line
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NODE_ENV=production node app.js
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<title>Set an environment variable inline when running Node.js - Interactive Tutorial</title>
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</style>
</head>
<body>
<div class="progress-container">
<div class="progress-bar" id="progressBar"></div>
</div>
<div class="hero">
<div class="hero-content">
<div class="env-icon">🌍</div>
<h1>Master Environment Variables!</h1>
<div class="command-display">NODE_ENV=production node app.js</div>
<p>Set environment variables inline! 🚀</p>
</div>
</div>
<div class="container">
<!-- What Is It -->
<section class="section">
<h2 class="section-title">🤔 What Is This Command?</h2>
<div class="card">
<p style="font-size: 1.2rem; margin-bottom: 20px;">
This command sets an <span class="highlight">environment variable</span> called <code>NODE_ENV</code> to <strong>"production"</strong> and then runs your Node.js application! 🌍
</p>
<p style="margin-bottom: 20px;">
Think of environment variables like sticky notes you attach to your app before it starts! 📝 They tell your application how to behave - whether it's running in development mode (on your laptop) or production mode (on a live server)!
</p>
<div class="info">
<strong>Breaking It Down:</strong>
<ul style="margin-left: 30px; margin-top: 10px; line-height: 2;">
<li><code class="code-env">NODE_ENV=production</code> - Sets the environment variable</li>
<li><code>node</code> - The Node.js runtime</li>
<li><code>app.js</code> - Your application file</li>
<li>The variable is available as <code>process.env.NODE_ENV</code> in your code</li>
</ul>
</div>
<div style="margin-top: 30px;">
<h3 style="color: var(--accent-pink); margin-bottom: 15px;">Why inline? 🔍</h3>
<p>Setting it inline means it's <strong>temporary</strong> - only for this one command! It won't affect other terminal sessions or persist after the app stops.</p>
</div>
<div style="margin-top: 20px;">
<span class="env-badge env-dev">development</span>
<span class="env-badge env-prod">production</span>
<span class="env-badge env-test">test</span>
</div>
</div>
</section>
<!-- Why Use It -->
<section class="section">
<h2 class="section-title">✨ Why Use Environment Variables?</h2>
<div class="card">
<div class="feature-grid">
<div class="feature-card">
<div class="feature-icon">🔧</div>
<div class="feature-title">Different Behaviors</div>
<p style="color: var(--text-secondary);">Dev vs Production modes!</p>
</div>
<div class="feature-card">
<div class="feature-icon">🔒</div>
<div class="feature-title">Security</div>
<p style="color: var(--text-secondary);">Hide sensitive data!</p>
</div>
<div class="feature-card">
<div class="feature-icon">⚡</div>
<div class="feature-title">Performance</div>
<p style="color: var(--text-secondary);">Optimize for production!</p>
</div>
<div class="feature-card">
<div class="feature-icon">🎯</div>
<div class="feature-title">Configuration</div>
<p style="color: var(--text-secondary);">Easy environment setup!</p>
</div>
<div class="feature-card">
<div class="feature-icon">🔄</div>
<div class="feature-title">Flexibility</div>
<p style="color: var(--text-secondary);">Change without code edits!</p>
</div>
<div class="feature-card">
<div class="feature-icon">✅</div>
<div class="feature-title">Best Practice</div>
<p style="color: var(--text-secondary);">Industry standard!</p>
</div>
</div>
</div>
</section>
<!-- How It Works -->
<section class="section">
<h2 class="section-title">⚙️ How Does It Work?</h2>
<div class="card">
<div class="steps">
<div class="step">
<h3>Step 1: Shell Reads Command</h3>
<p>Your terminal (bash/zsh) parses the command line.</p>
</div>
<div class="step">
<h3>Step 2: Sets Environment Variable</h3>
<p>Creates NODE_ENV variable with value "production" for this process.</p>
</div>
<div class="step">
<h3>Step 3: Starts Node.js</h3>
<p>Launches the Node.js runtime with the environment variable.</p>
</div>
<div class="step">
<h3>Step 4: Loads Your App</h3>
<p>Node.js executes app.js with access to process.env.NODE_ENV.</p>
</div>
<div class="step">
<h3>Step 5: App Reads Variable</h3>
<p>Your code can check the value and behave accordingly.</p>
</div>
<div class="step">
<h3>Step 6: Variable Disappears</h3>
<p>When app stops, the variable is gone! 🎉</p>
</div>
</div>
</div>
</section>
<!-- Live Demo -->
<section class="section">
<h2 class="section-title">🎮 Interactive Demo</h2>
<div class="demo-container">
<h3 style="margin-bottom: 20px; font-size: 1.5rem;">See It In Action! 🚀</h3>
<button class="demo-button" onclick="simulateProduction()">
<span>🔴</span>
<span>Run in Production</span>
</button>
<button class="demo-button" onclick="simulateDevelopment()">
<span>🔵</span>
<span>Run in Development</span>
</button>
<button class="demo-button" onclick="simulateMultipleVars()">
<span>🌈</span>
<span>Multiple Variables</span>
</button>
<div class="terminal" id="terminal">
<div class="terminal-line">
<span class="terminal-prompt">$</span>
<span style="color: var(--text-secondary);"> Ready to run your app...</span>
</div>
</div>
</div>
</section>
<!-- Code Breakdown -->
<section class="section">
<h2 class="section-title">💻 Command Variations</h2>
<div class="card">
<div class="tabs">
<button class="tab active" onclick="switchTab('basic')">Basic Usage</button>
<button class="tab" onclick="switchTab('multiple')">Multiple Variables</button>
<button class="tab" onclick="switchTab('windows')">Windows</button>
<button class="tab" onclick="switchTab('dotenv')">Using .env Files</button>
</div>
<div id="basic" class="tab-content active">
<h3 style="color: var(--accent-pink); margin-bottom: 15px;">Basic Environment Variable</h3>
<div class="code-block">
<div class="code-header">
<div class="terminal-dots">
<div class="terminal-dot dot-red"></div>
<div class="terminal-dot dot-yellow"></div>
<div class="terminal-dot dot-green"></div>
</div>
<button class="copy-btn" onclick="copyCode('basic-code')">📋 Copy</button>
</div>
<pre><code id="basic-code"><span class="code-comment"># Set NODE_ENV to production (Linux/Mac)</span>
NODE_ENV=production node app.js
<span class="code-comment"># Set to development</span>
NODE_ENV=development node app.js
<span class="code-comment"># Set to test</span>
NODE_ENV=test node app.js
<span class="code-comment"># Access in your code:</span>
console.log(process.env.NODE_ENV); <span class="code-comment">// "production"</span></code></pre>
</div>
<div class="success" style="margin-top: 15px;">
<strong>Result:</strong> Your app knows what environment it's running in!
</div>
</div>
<div id="multiple" class="tab-content">
<h3 style="color: var(--accent-pink); margin-bottom: 15px;">Multiple Environment Variables</h3>
<div class="code-block">
<div class="code-header">
<div class="terminal-dots">
<div class="terminal-dot dot-red"></div>
<div class="terminal-dot dot-yellow"></div>
<div class="terminal-dot dot-green"></div>
</div>
<button class="copy-btn" onclick="copyCode('multiple-code')">📋 Copy</button>
</div>
<pre><code id="multiple-code"><span class="code-comment"># Set multiple variables at once</span>
NODE_ENV=production PORT=3000 DEBUG=false node app.js
<span class="code-comment"># With database URL</span>
NODE_ENV=production DB_URL=mongodb://localhost:27017 node app.js
<span class="code-comment"># Access in code:</span>
const env = process.env.NODE_ENV;
const port = process.env.PORT;
const debug = process.env.DEBUG;</code></pre>
</div>
<div class="tip" style="margin-top: 15px;">
<strong>Pro Tip:</strong> Separate multiple variables with spaces!
</div>
</div>
<div id="windows" class="tab-content">
<h3 style="color: var(--accent-pink); margin-bottom: 15px;">Windows Command Prompt</h3>
<div class="code-block">
<div class="code-header">
<div class="terminal-dots">
<div class="terminal-dot dot-red"></div>
<div class="terminal-dot dot-yellow"></div>
<div class="terminal-dot dot-green"></div>
</div>
<button class="copy-btn" onclick="copyCode('windows-code')">📋 Copy</button>
</div>
<pre><code id="windows-code"><span class="code-comment"># Windows CMD (different syntax!)</span>
set NODE_ENV=production && node app.js
<span class="code-comment"># Windows PowerShell</span>
$env:NODE_ENV="production"; node app.js
<span class="code-comment"># Cross-platform solution (use cross-env package)</span>
npm install --save-dev cross-env
cross-env NODE_ENV=production node app.js</code></pre>
</div>
<div class="warning" style="margin-top: 15px;">
<strong>Important:</strong> Windows uses different syntax! Use <code>cross-env</code> for cross-platform compatibility.
</div>
</div>
<div id="dotenv" class="tab-content">
<h3 style="color: var(--accent-pink); margin-bottom: 15px;">Using .env Files</h3>
<div class="code-block">
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<button class="copy-btn" onclick="copyCode('dotenv-code')">📋 Copy</button>
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<pre><code id="dotenv-code"><span class="code-comment"># Install dotenv package</span>
npm install dotenv
<span class="code-comment"># Create .env file</span>
NODE_ENV=production
PORT=3000
DB_URL=mongodb://localhost:27017
<span class="code-comment"># In your app.js</span>
require('dotenv').config();
console.log(process.env.NODE_ENV); <span class="code-comment">// "production"</span>
<span class="code-comment"># Run normally</span>
node app.js</code></pre>
</div>
<div class="info" style="margin-top: 15px;">
<strong>Note:</strong> .env files are better for managing many variables! Don't commit them to git!
</div>
</div>
</div>
</section>
<!-- Common Mistakes -->
<section class="section">
<h2 class="section-title">❌ Common Mistakes</h2>
<div class="card">
<div class="accordion">
<div class="accordion-item">
<div class="accordion-header" onclick="toggleAccordion(this)">
<span><strong>1. Using Windows Syntax on Mac/Linux</strong></span>
<span class="accordion-icon">▼</span>
</div>
<div class="accordion-content">
<div class="accordion-body">
<div class="warning">
<strong>Problem:</strong> <code>set NODE_ENV=production</code> doesn't work on Mac/Linux!
</div>
<div class="success" style="margin-top: 15px;">
<strong>Solution:</strong> Use <code>NODE_ENV=production</code> (no "set") or install <code>cross-env</code>!
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<span><strong>2. Spaces Around the Equals Sign</strong></span>
<span class="accordion-icon">▼</span>
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<div class="warning">
<strong>Problem:</strong> <code>NODE_ENV = production</code> won't work!
</div>
<div class="success" style="margin-top: 15px;">
<strong>Solution:</strong> No spaces! Use <code>NODE_ENV=production</code>
</div>
</div>
</div>
</div>
<div class="accordion-item">
<div class="accordion-header" onclick="toggleAccordion(this)">
<span><strong>3. Forgetting to Check the Variable</strong></span>
<span class="accordion-icon">▼</span>
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<div class="accordion-body">
<div class="warning">
<strong>Problem:</strong> Setting the variable but not using it in your code!
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<strong>Solution:</strong> Always check: <code>if (process.env.NODE_ENV === 'production') { ... }</code>
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<th>Environment</th>
<th>Purpose</th>
<th>Typical Settings</th>
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<td><span class="env-badge env-dev">development</span></td>
<td>Local development</td>
<td>Debug on, verbose logs, hot reload</td>
</tr>
<tr>
<td><span class="env-badge env-prod">production</span></td>
<td>Live server</td>
<td>Optimized, minified, error tracking</td>
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<tr>
<td><span class="env-badge env-test">test</span></td>
<td>Running tests</td>
<td>Test database, mock services</td>
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<h2 class="section-title">🚀 Pro Tips</h2>
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<strong>Use cross-env for compatibility</strong> - Works on Windows, Mac, and Linux!
</div>
<div class="tip">
<strong>Create npm scripts</strong> - Add to package.json: <code>"start": "NODE_ENV=production node app.js"</code>
</div>
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<strong>Use .env files</strong> - Better for managing multiple variables with dotenv package!
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<strong>Never commit secrets</strong> - Add .env to .gitignore! Use .env.example instead.
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<strong>Validate environment</strong> - Check if NODE_ENV is set: <code>process.env.NODE_ENV || 'development'</code>
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<strong>Use strict equality</strong> - Always use <code>===</code> when checking: <code>NODE_ENV === 'production'</code>
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<h3>Question 1: How do you access NODE_ENV in your code?</h3>
<div class="quiz-options">
<div class="quiz-option" onclick="checkAnswer(this, false, 1)">A) NODE_ENV</div>
<div class="quiz-option" onclick="checkAnswer(this, true, 1)">B) process.env.NODE_ENV</div>
<div class="quiz-option" onclick="checkAnswer(this, false, 1)">C) env.NODE_ENV</div>
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<h3>Question 2: What's the correct syntax for Mac/Linux?</h3>
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<div class="quiz-option" onclick="checkAnswer(this, false, 2)">A) set NODE_ENV=production node app.js</div>
<div class="quiz-option" onclick="checkAnswer(this, true, 2)">B) NODE_ENV=production node app.js</div>
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<div class="quiz-option" onclick="checkAnswer(this, true, 3)">B) cross-env</div>
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<h2 class="section-title">📚 Quick Reference</h2>
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<h3 style="margin-bottom: 20px; font-size: 2rem;">Environment Variables Cheat Sheet! 🔖</h3>
<div class="cheat-grid">
<div class="cheat-item">
<h4>🐧 Linux/Mac</h4>
<p><code>NODE_ENV=production node app.js</code></p>
<p style="font-size: 0.85rem; margin-top: 5px;">Standard syntax</p>
</div>
<div class="cheat-item">
<h4>🪟 Windows CMD</h4>
<p><code>set NODE_ENV=production && node app.js</code></p>
<p style="font-size: 0.85rem; margin-top: 5px;">Windows syntax</p>
</div>
<div class="cheat-item">
<h4>🌈 Cross-Platform</h4>
<p><code>cross-env NODE_ENV=production node app.js</code></p>
<p style="font-size: 0.85rem; margin-top: 5px;">Works everywhere</p>
</div>
<div class="cheat-item">
<h4>📦 Multiple Vars</h4>
<p><code>VAR1=val1 VAR2=val2 node app.js</code></p>
<p style="font-size: 0.85rem; margin-top: 5px;">Space separated</p>
</div>
<div class="cheat-item">
<h4>📄 Access in Code</h4>
<p><code>process.env.NODE_ENV</code></p>
<p style="font-size: 0.85rem; margin-top: 5px;">Read the value</p>
</div>
<div class="cheat-item">
<h4>🔧 npm Script</h4>
<p><code>"start": "NODE_ENV=prod node app.js"</code></p>
<p style="font-size: 0.85rem; margin-top: 5px;">In package.json</p>
</div>
<div class="cheat-item">
<h4>📝 .env File</h4>
<p><code>require('dotenv').config()</code></p>
<p style="font-size: 0.85rem; margin-top: 5px;">Load from file</p>
</div>
<div class="cheat-item">
<h4>✅ Common Values</h4>
<p>development, production, test</p>
<p style="font-size: 0.85rem; margin-top: 5px;">Standard names</p>
</div>
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</div>
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<p style="font-size: 1.2rem; margin-bottom: 20px;">You now understand <strong>environment variables</strong>! 🚀</p>
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