Require a module before executing the main script
📦 Node.js-> Command Line
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node -r dotenv/config app.js
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<!DOCTYPE html>
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<head>
<meta charset="UTF-8">
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<title>Require a module before executing the main script - Interactive Tutorial</title>
<link href="https://fonts.googleapis.com/css2?family=Poppins:wght@300;400;600;700;900&family=Fira+Code:wght@400;500;600&display=swap" rel="stylesheet">
<style>
:root {
--bg-primary: #0a0e27;
--bg-secondary: #151932;
--bg-card: #1e2139;
--accent-purple: #a855f7;
--accent-blue: #3b82f6;
--accent-green: #10b981;
--accent-red: #ef4444;
--accent-yellow: #f59e0b;
--accent-pink: #ec4899;
--accent-cyan: #06b6d4;
--accent-lime: #84cc16;
--text-primary: #f8fafc;
--text-secondary: #94a3b8;
--gradient-env: linear-gradient(135deg, #84cc16 0%, #10b981 100%);
--gradient-node: linear-gradient(135deg, #10b981 0%, #06b6d4 100%);
--shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
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* {
margin: 0;
padding: 0;
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body {
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background: var(--bg-primary);
color: var(--text-primary);
line-height: 1.6;
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.container {
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padding: 20px;
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.progress-container {
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height: 5px;
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z-index: 1000;
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.progress-bar {
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.hero {
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.hero::before {
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animation: float 20s linear infinite;
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@keyframes float {
from { transform: translateY(0); }
to { transform: translateY(-100px); }
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.hero-content {
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z-index: 1;
}
.env-icon {
font-size: 5rem;
margin-bottom: 20px;
animation: envPulse 3s ease-in-out infinite;
}
@keyframes envPulse {
0%, 100% { transform: scale(1) rotate(0deg); }
50% { transform: scale(1.15) rotate(5deg); }
}
.command-display {
display: inline-block;
background: rgba(0, 0, 0, 0.4);
padding: 25px 40px;
border-radius: 15px;
font-family: 'Fira Code', monospace;
font-size: 1.2rem;
margin: 30px 0;
border: 3px solid rgba(255, 255, 255, 0.3);
animation: pulse 2s ease-in-out infinite;
color: white;
font-weight: 600;
}
@keyframes pulse {
0%, 100% { transform: scale(1); }
50% { transform: scale(1.05); }
}
.hero h1 {
font-size: 3.5rem;
font-weight: 900;
margin-bottom: 20px;
color: white;
text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
}
.hero p {
font-size: 1.4rem;
opacity: 0.95;
color: white;
}
.section {
margin: 60px 0;
}
.section-title {
font-size: 2.5rem;
margin-bottom: 30px;
background: var(--gradient-env);
-webkit-background-clip: text;
-webkit-text-fill-color: transparent;
background-clip: text;
display: inline-block;
font-weight: 700;
}
.card {
background: var(--bg-card);
border-radius: 20px;
padding: 40px;
margin: 30px 0;
box-shadow: var(--shadow);
border: 1px solid rgba(255, 255, 255, 0.05);
transition: transform 0.3s ease;
}
.card:hover {
transform: translateY(-5px);
}
.code-block {
background: #1e1e1e;
border-radius: 15px;
padding: 25px;
margin: 20px 0;
font-family: 'Fira Code', monospace;
position: relative;
}
.code-header {
display: flex;
justify-content: space-between;
align-items: center;
margin-bottom: 15px;
padding-bottom: 15px;
border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}
.terminal-dots {
display: flex;
gap: 6px;
}
.terminal-dot {
width: 12px;
height: 12px;
border-radius: 50%;
}
.dot-red { background: #ff5f56; }
.dot-yellow { background: #ffbd2e; }
.dot-green { background: #27c93f; }
.copy-btn {
background: var(--accent-purple);
color: white;
border: none;
padding: 8px 16px;
border-radius: 8px;
cursor: pointer;
font-size: 0.9rem;
transition: all 0.3s ease;
}
.copy-btn:hover {
background: var(--accent-blue);
transform: scale(1.05);
}
.copy-btn.copied {
background: var(--accent-green);
}
pre {
margin: 0;
overflow-x: auto;
}
code {
color: #e0e0e0;
font-size: 0.95rem;
line-height: 1.8;
}
.code-comment { color: #6a9955; }
.code-string { color: #ce9178; }
.code-keyword { color: #569cd6; }
.code-node { color: #84cc16; font-weight: 600; }
.code-flag { color: #10b981; font-weight: 600; }
.code-env { color: #f59e0b; font-weight: 600; }
.steps {
counter-reset: step-counter;
}
.step {
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border-radius: 15px;
padding: 30px;
margin: 20px 0;
position: relative;
padding-left: 100px;
transition: all 0.3s ease;
}
.step:hover {
background: var(--bg-card);
transform: translateX(10px);
}
.step::before {
counter-increment: step-counter;
content: counter(step-counter);
position: absolute;
left: 20px;
top: 50%;
transform: translateY(-50%);
width: 60px;
height: 60px;
background: var(--gradient-env);
border-radius: 50%;
display: flex;
align-items: center;
justify-content: center;
font-size: 1.8rem;
font-weight: 900;
color: white;
}
.step h3 {
color: var(--accent-lime);
margin-bottom: 10px;
font-size: 1.5rem;
}
.feature-grid {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
gap: 25px;
margin: 30px 0;
}
.feature-card {
background: var(--bg-secondary);
padding: 30px;
border-radius: 15px;
text-align: center;
transition: all 0.3s ease;
border: 2px solid transparent;
}
.feature-card:hover {
border-color: var(--accent-lime);
transform: translateY(-10px);
}
.feature-icon {
font-size: 3.5rem;
margin-bottom: 15px;
}
.feature-title {
font-weight: 600;
color: var(--accent-lime);
margin-bottom: 10px;
font-size: 1.3rem;
}
.demo-container {
background: var(--bg-secondary);
border-radius: 20px;
padding: 40px;
margin: 30px 0;
}
.env-simulator {
background: var(--bg-card);
border-radius: 15px;
padding: 30px;
margin: 30px 0;
border: 2px solid var(--accent-lime);
}
.env-file {
background: #1e1e1e;
border-radius: 10px;
padding: 20px;
margin: 15px 0;
font-family: 'Fira Code', monospace;
border-left: 4px solid var(--accent-lime);
}
.terminal {
background: #1e1e1e;
border-radius: 15px;
padding: 20px;
font-family: 'Fira Code', monospace;
min-height: 250px;
margin: 20px 0;
overflow-y: auto;
max-height: 500px;
}
.terminal-line {
margin: 10px 0;
}
.terminal-prompt {
color: var(--accent-green);
}
.terminal-success {
color: var(--accent-green);
font-weight: 600;
}
.demo-button {
background: var(--gradient-env);
color: white;
border: none;
padding: 15px 40px;
border-radius: 50px;
font-size: 1.1rem;
font-weight: 600;
cursor: pointer;
transition: all 0.3s ease;
display: inline-flex;
align-items: center;
gap: 10px;
margin: 10px;
}
.demo-button:hover {
transform: scale(1.05);
box-shadow: 0 10px 30px rgba(132, 204, 22, 0.4);
}
.flow-diagram {
display: flex;
align-items: center;
justify-content: center;
gap: 20px;
margin: 30px 0;
flex-wrap: wrap;
}
.flow-box {
background: var(--bg-secondary);
padding: 20px 30px;
border-radius: 12px;
border: 2px solid var(--accent-lime);
text-align: center;
min-width: 150px;
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.flow-arrow {
font-size: 2rem;
color: var(--accent-lime);
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.tabs {
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gap: 10px;
margin-bottom: 20px;
flex-wrap: wrap;
}
.tab {
padding: 12px 24px;
background: var(--bg-secondary);
border: none;
border-radius: 10px;
color: var(--text-primary);
cursor: pointer;
transition: all 0.3s ease;
font-size: 1rem;
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.tab:hover {
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}
.tab.active {
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color: white;
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.tab-content {
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}
.tab-content.active {
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.accordion-header {
cursor: pointer;
display: flex;
justify-content: space-between;
align-items: center;
padding: 20px;
background: var(--bg-secondary);
border-radius: 12px;
margin: 15px 0;
transition: all 0.3s ease;
}
.accordion-header:hover {
background: var(--bg-card);
}
.accordion-icon {
transition: transform 0.3s ease;
font-size: 1.2rem;
}
.accordion-icon.active {
transform: rotate(180deg);
}
.accordion-content {
max-height: 0;
overflow: hidden;
transition: max-height 0.3s ease;
}
.accordion-content.active {
max-height: 2000px;
}
.accordion-body {
padding: 20px;
background: var(--bg-secondary);
border-radius: 12px;
margin-top: 5px;
}
.tip, .warning, .success, .info {
padding: 20px;
border-radius: 10px;
margin: 20px 0;
}
.tip {
background: rgba(59, 130, 246, 0.1);
border-left: 4px solid var(--accent-blue);
}
.tip::before { content: '💡 '; font-size: 1.5rem; }
.warning {
background: rgba(239, 68, 68, 0.1);
border-left: 4px solid var(--accent-red);
}
.warning::before { content: '⚠️ '; font-size: 1.5rem; }
.success {
background: rgba(16, 185, 129, 0.1);
border-left: 4px solid var(--accent-green);
}
.success::before { content: '✅ '; font-size: 1.5rem; }
.info {
background: rgba(236, 72, 153, 0.1);
border-left: 4px solid var(--accent-pink);
}
.info::before { content: '🔍 '; font-size: 1.5rem; }
.quiz-container {
background: var(--bg-card);
border-radius: 20px;
padding: 40px;
margin: 30px 0;
}
.quiz-question {
margin: 30px 0;
}
.quiz-question h3 {
color: var(--accent-purple);
margin-bottom: 20px;
font-size: 1.3rem;
}
.quiz-options {
display: flex;
flex-direction: column;
gap: 15px;
}
.quiz-option {
background: var(--bg-secondary);
padding: 20px;
border-radius: 12px;
cursor: pointer;
transition: all 0.3s ease;
border: 2px solid transparent;
}
.quiz-option:hover {
border-color: var(--accent-blue);
transform: translateX(10px);
}
.quiz-option.correct {
border-color: var(--accent-green);
background: rgba(16, 185, 129, 0.1);
}
.quiz-option.incorrect {
border-color: var(--accent-red);
background: rgba(239, 68, 68, 0.1);
}
.quiz-feedback {
margin-top: 15px;
padding: 15px;
border-radius: 10px;
display: none;
}
.quiz-feedback.show {
display: block;
}
.quiz-feedback.correct {
background: rgba(16, 185, 129, 0.1);
border-left: 4px solid var(--accent-green);
}
.quiz-feedback.incorrect {
background: rgba(239, 68, 68, 0.1);
border-left: 4px solid var(--accent-red);
}
.cheat-sheet {
background: var(--gradient-env);
border-radius: 20px;
padding: 40px;
margin: 30px 0;
color: white;
}
.cheat-grid {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
gap: 20px;
margin-top: 30px;
}
.cheat-item {
background: rgba(255, 255, 255, 0.15);
backdrop-filter: blur(10px);
padding: 20px;
border-radius: 15px;
border: 1px solid rgba(255, 255, 255, 0.2);
}
.cheat-item h4 {
color: white;
margin-bottom: 10px;
font-weight: 600;
}
.cheat-item code {
background: rgba(0, 0, 0, 0.3);
padding: 4px 8px;
border-radius: 5px;
font-size: 0.9rem;
color: white;
}
.highlight {
color: var(--accent-yellow);
font-weight: 600;
}
.footer {
text-align: center;
padding: 40px 20px;
background: var(--bg-secondary);
margin-top: 80px;
border-radius: 20px;
}
.footer p {
color: var(--text-secondary);
margin: 10px 0;
}
.badge {
display: inline-block;
padding: 6px 12px;
background: var(--gradient-env);
border-radius: 20px;
font-size: 0.85rem;
font-weight: 600;
margin: 5px;
}
.confetti {
position: fixed;
width: 10px;
height: 10px;
background: var(--accent-lime);
animation: confetti-fall 3s linear forwards;
z-index: 9999;
}
@keyframes confetti-fall {
to {
transform: translateY(100vh) rotate(360deg);
opacity: 0;
}
}
@media (max-width: 768px) {
.hero h1 { font-size: 2rem; }
.command-display { font-size: 0.9rem; padding: 15px 20px; }
.section-title { font-size: 1.8rem; }
.card { padding: 25px; }
.step { padding-left: 80px; }
.step::before { width: 50px; height: 50px; font-size: 1.5rem; }
.flow-diagram { flex-direction: column; }
}
</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 Node -r Flag!</h1>
<div class="command-display">node -r dotenv/config app.js</div>
<p>Preload modules before your app starts! 🚀</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 runs your Node.js app (<code>app.js</code>) but <span class="highlight">first loads the dotenv/config module</span>, which reads your <code>.env</code> file and injects environment variables into <code>process.env</code>! 🌱
</p>
<p style="margin-bottom: 20px;">
Think of it like putting on your shoes BEFORE leaving the house! 👟 The <code>-r</code> flag (short for <code>--require</code>) tells Node: "Hey, load this module first, THEN run my app." It's perfect for loading configuration, environment variables, or any setup code before your main script executes!
</p>
<div class="info">
<strong>Breaking It Down:</strong>
<ul style="margin-left: 30px; margin-top: 10px; line-height: 2;">
<li><code class="code-node">node</code> - Node.js runtime</li>
<li><code class="code-flag">-r</code> - Require/preload a module (alias for --require)</li>
<li><code class="code-env">dotenv/config</code> - Module that loads .env file</li>
<li><code>app.js</code> - Your main application file</li>
<li>Order: dotenv loads FIRST, then app.js runs</li>
</ul>
</div>
<div style="margin-top: 30px;">
<h3 style="color: var(--accent-pink); margin-bottom: 15px;">What's dotenv? 🔍</h3>
<p>dotenv is a popular npm package that loads environment variables from a <code>.env</code> file into <code>process.env</code>. Instead of hardcoding secrets like API keys, you store them in <code>.env</code> and dotenv makes them available to your app!</p>
</div>
</div>
</section>
<!-- Flow Diagram -->
<section class="section">
<h2 class="section-title">🔄 Execution Flow</h2>
<div class="card">
<h3 style="margin-bottom: 20px; text-align: center;">See How It Works! 🎯</h3>
<div class="flow-diagram">
<div class="flow-box">
<div style="font-size: 2rem; margin-bottom: 10px;">📄</div>
<strong>.env file</strong>
<p style="font-size: 0.85rem; color: var(--text-secondary); margin-top: 5px;">API_KEY=secret</p>
</div>
<div class="flow-arrow">→</div>
<div class="flow-box">
<div style="font-size: 2rem; margin-bottom: 10px;">🌱</div>
<strong>dotenv/config</strong>
<p style="font-size: 0.85rem; color: var(--text-secondary); margin-top: 5px;">Loads first</p>
</div>
<div class="flow-arrow">→</div>
<div class="flow-box">
<div style="font-size: 2rem; margin-bottom: 10px;">⚙️</div>
<strong>process.env</strong>
<p style="font-size: 0.85rem; color: var(--text-secondary); margin-top: 5px;">Variables available</p>
</div>
<div class="flow-arrow">→</div>
<div class="flow-box">
<div style="font-size: 2rem; margin-bottom: 10px;">🚀</div>
<strong>app.js</strong>
<p style="font-size: 0.85rem; color: var(--text-secondary); margin-top: 5px;">Runs with env vars</p>
</div>
</div>
</div>
</section>
<!-- Why Use It -->
<section class="section">
<h2 class="section-title">✨ Why Use -r Flag?</h2>
<div class="card">
<div class="feature-grid">
<div class="feature-card">
<div class="feature-icon">🔒</div>
<div class="feature-title">Security</div>
<p style="color: var(--text-secondary);">Keep secrets out of code!</p>
</div>
<div class="feature-card">
<div class="feature-icon">🧹</div>
<div class="feature-title">Clean Code</div>
<p style="color: var(--text-secondary);">No require() in app!</p>
</div>
<div class="feature-card">
<div class="feature-icon">⚡</div>
<div class="feature-title">Early Loading</div>
<p style="color: var(--text-secondary);">Config ready before app!</p>
</div>
<div class="feature-card">
<div class="feature-icon">🔄</div>
<div class="feature-title">Reusable</div>
<p style="color: var(--text-secondary);">Works with any module!</p>
</div>
<div class="feature-card">
<div class="feature-icon">🎯</div>
<div class="feature-title">No Code Changes</div>
<p style="color: var(--text-secondary);">CLI-level configuration!</p>
</div>
<div class="feature-card">
<div class="feature-icon">🛠️</div>
<div class="feature-title">Debugging</div>
<p style="color: var(--text-secondary);">Load debug tools first!</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: Node Starts</h3>
<p>Node.js runtime begins execution.</p>
</div>
<div class="step">
<h3>Step 2: Parse -r Flag</h3>
<p>Node sees -r dotenv/config flag.</p>
</div>
<div class="step">
<h3>Step 3: Load dotenv/config</h3>
<p>Requires and executes dotenv/config module.</p>
</div>
<div class="step">
<h3>Step 4: Read .env File</h3>
<p>dotenv reads .env file from current directory.</p>
</div>
<div class="step">
<h3>Step 5: Inject Variables</h3>
<p>Environment variables added to process.env.</p>
</div>
<div class="step">
<h3>Step 6: Run app.js</h3>
<p>Your app starts with all env vars available! 🎉</p>
</div>
</div>
</div>
</section>
<!-- Live Demo -->
<section class="section">
<h2 class="section-title">🎮 Interactive Demo</h2>
<div class="demo-container">
<div class="env-simulator">
<h3 style="margin-bottom: 20px;">See It In Action! 🌱</h3>
<div class="env-file">
<div style="color: var(--accent-lime); margin-bottom: 10px; font-weight: 600;">.env file:</div>
<div style="color: var(--text-secondary);">API_KEY=super_secret_key_123</div>
<div style="color: var(--text-secondary);">DB_HOST=localhost</div>
<div style="color: var(--text-secondary);">PORT=3000</div>
</div>
</div>
<div style="margin-top: 30px; text-align: center;">
<h4 style="margin-bottom: 15px;">Try Different Scenarios! 🔍</h4>
<button class="demo-button" onclick="simulateWithDotenv()">
<span>✅</span>
<span>With -r dotenv/config</span>
</button>
<button class="demo-button" onclick="simulateWithoutDotenv()">
<span>❌</span>
<span>Without -r flag</span>
</button>
<button class="demo-button" onclick="simulateMultipleModules()">
<span>🔄</span>
<span>Multiple -r flags</span>
</button>
</div>
<div class="terminal" id="terminal">
<div class="terminal-line">
<span class="terminal-prompt">$</span>
<span style="color: var(--text-secondary);"> Ready to run Node.js...</span>
</div>
</div>
</div>
</section>
<!-- Code Breakdown -->
<section class="section">
<h2 class="section-title">💻 Usage Examples</h2>
<div class="card">
<div class="tabs">
<button class="tab active" onclick="switchTab('basic')">Basic Usage</button>
<button class="tab" onclick="switchTab('multiple')">Multiple Modules</button>
<button class="tab" onclick="switchTab('alternatives')">Alternatives</button>
<button class="tab" onclick="switchTab('package')">package.json</button>
</div>
<div id="basic" class="tab-content active">
<h3 style="color: var(--accent-pink); margin-bottom: 15px;">Basic dotenv Usage</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"># Run with dotenv preloaded</span>
node -r dotenv/config app.js
<span class="code-comment"># Long form (same thing)</span>
node --require dotenv/config app.js
<span class="code-comment"># Now in app.js, you can access:</span>
console.log(process.env.API_KEY); <span class="code-comment">// 'super_secret_key_123'</span>
console.log(process.env.PORT); <span class="code-comment">// '3000'</span></code></pre>
</div>
<div class="success" style="margin-top: 15px;">
<strong>Result:</strong> Environment variables loaded before your app runs!
</div>
</div>
<div id="multiple" class="tab-content">
<h3 style="color: var(--accent-pink); margin-bottom: 15px;">Load Multiple Modules</h3>
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<pre><code id="multiple-code"><span class="code-comment"># Load multiple modules in order</span>
node -r dotenv/config -r ./setup.js -r module-alias/register app.js
<span class="code-comment"># They load in order: dotenv → setup.js → module-alias → app.js</span>
<span class="code-comment"># Common use case: Load env + path aliases</span>
node -r dotenv/config -r tsconfig-paths/register app.js
<span class="code-comment"># For TypeScript with ts-node</span>
node -r ts-node/register -r dotenv/config app.ts</code></pre>
</div>
<div class="tip" style="margin-top: 15px;">
<strong>Pro Tip:</strong> You can chain multiple -r flags! They execute left to right.
</div>
</div>
<div id="alternatives" class="tab-content">
<h3 style="color: var(--accent-pink); margin-bottom: 15px;">Alternative Approaches</h3>
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<pre><code id="alternatives-code"><span class="code-comment">// Method 1: Using -r flag (recommended)</span>
<span class="code-comment">// Command: node -r dotenv/config app.js</span>
<span class="code-comment">// app.js - no dotenv import needed!</span>
console.log(process.env.API_KEY);
<span class="code-comment">// Method 2: Import in code (traditional)</span>
<span class="code-keyword">require</span>(<span class="code-string">'dotenv'</span>).config();
console.log(process.env.API_KEY);
<span class="code-comment">// Method 3: ES modules</span>
<span class="code-keyword">import</span> <span class="code-string">'dotenv/config'</span>;
console.log(process.env.API_KEY);
<span class="code-comment">// Method 4: NODE_OPTIONS environment variable</span>
<span class="code-comment">// In terminal or .env:</span>
NODE_OPTIONS=<span class="code-string">'-r dotenv/config'</span>
node app.js</code></pre>
</div>
</div>
<div id="package" class="tab-content">
<h3 style="color: var(--accent-pink); margin-bottom: 15px;">Add to package.json Scripts</h3>
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<pre><code id="package-code"><span class="code-comment">// package.json</span>
{
<span class="code-string">"name"</span>: <span class="code-string">"my-app"</span>,
<span class="code-string">"scripts"</span>: {
<span class="code-string">"start"</span>: <span class="code-string">"node -r dotenv/config app.js"</span>,
<span class="code-string">"dev"</span>: <span class="code-string">"nodemon -r dotenv/config app.js"</span>,
<span class="code-string">"test"</span>: <span class="code-string">"node -r dotenv/config test.js"</span>
}
}
<span class="code-comment"># Now just run:</span>
npm start <span class="code-comment"># Runs with dotenv loaded</span>
npm run dev <span class="code-comment"># Dev mode with dotenv</span>
npm test <span class="code-comment"># Tests with dotenv</span></code></pre>
</div>
<div class="success" style="margin-top: 15px;">
<strong>Best Practice:</strong> Add -r dotenv/config to your npm scripts!
</div>
</div>
</div>
</section>
<!-- Common Mistakes -->
<section class="section">
<h2 class="section-title">❌ Common Mistakes</h2>
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<div class="accordion-item">
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<span><strong>1. Wrong Module Path</strong></span>
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<div class="warning">
<strong>Problem:</strong> Using <code>-r dotenv</code> instead of <code>-r dotenv/config</code>
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<div class="success" style="margin-top: 15px;">
<strong>Solution:</strong> Use <code>dotenv/config</code> - it auto-runs config()!
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<span><strong>2. Missing .env File</strong></span>
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<div class="warning">
<strong>Problem:</strong> .env file not in project root
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<strong>Solution:</strong> Ensure .env is in the directory where you run node!
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<span><strong>3. Package Not Installed</strong></span>
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<div class="warning">
<strong>Problem:</strong> Error: Cannot find module 'dotenv/config'
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<div class="success" style="margin-top: 15px;">
<strong>Solution:</strong> Run <code>npm install dotenv</code> first!
</div>
</div>
</div>
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<div class="accordion-item">
<div class="accordion-header" onclick="toggleAccordion(this)">
<span><strong>4. Order Matters</strong></span>
<span class="accordion-icon">▼</span>
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<div class="accordion-body">
<div class="warning">
<strong>Problem:</strong> Putting -r flag after app.js
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<div class="success" style="margin-top: 15px;">
<strong>Solution:</strong> -r flag must come BEFORE app.js: <code>node -r dotenv/config app.js</code>
</div>
</div>
</div>
</div>
</div>
</div>
</section>
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<h2 class="section-title">🚀 Pro Tips</h2>
<div class="card">
<div class="tip">
<strong>Use in package.json</strong> - Add to scripts so team members don't forget!
</div>
<div class="tip">
<strong>Multiple environments</strong> - Use <code>dotenv/config</code> with different .env files!
</div>
<div class="tip">
<strong>Debugging</strong> - Load debug tools: <code>node -r dotenv/config -r ./debug.js app.js</code>
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<div class="tip">
<strong>TypeScript</strong> - Combine with ts-node: <code>node -r ts-node/register -r dotenv/config app.ts</code>
</div>
<div class="tip">
<strong>NODE_OPTIONS</strong> - Set globally: <code>export NODE_OPTIONS='-r dotenv/config'</code>
</div>
<div class="tip">
<strong>Clean code</strong> - No need to import dotenv in your app code!
</div>
<div class="tip">
<strong>Testing</strong> - Load test config before tests run!
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<h2 class="section-title">🎯 Knowledge Check Quiz</h2>
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<p style="margin-bottom: 30px; font-size: 1.1rem;">Test your understanding! 🧠</p>
<div class="quiz-question">
<h3>Question 1: What does -r flag do?</h3>
<div class="quiz-options">
<div class="quiz-option" onclick="checkAnswer(this, false, 1)">A) Runs the app in production mode</div>
<div class="quiz-option" onclick="checkAnswer(this, true, 1)">B) Requires/preloads a module before main script</div>
<div class="quiz-option" onclick="checkAnswer(this, false, 1)">C) Restarts the app automatically</div>
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<div class="quiz-feedback" id="feedback1"></div>
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<div class="quiz-question">
<h3>Question 2: What's the correct syntax?</h3>
<div class="quiz-options">
<div class="quiz-option" onclick="checkAnswer(this, false, 2)">A) node app.js -r dotenv/config</div>
<div class="quiz-option" onclick="checkAnswer(this, true, 2)">B) node -r dotenv/config app.js</div>
<div class="quiz-option" onclick="checkAnswer(this, false, 2)">C) node -r app.js dotenv/config</div>
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<h3>Question 3: Can you use multiple -r flags?</h3>
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<div class="quiz-option" onclick="checkAnswer(this, false, 3)">A) No, only one module allowed</div>
<div class="quiz-option" onclick="checkAnswer(this, true, 3)">B) Yes, they load in order left to right</div>
<div class="quiz-option" onclick="checkAnswer(this, false, 3)">C) Yes, but they load randomly</div>
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<!-- Summary Card -->
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<h2 class="section-title">📚 Quick Reference</h2>
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<h3 style="margin-bottom: 20px; font-size: 2rem;">node -r Cheat Sheet! 🔖</h3>
<div class="cheat-grid">
<div class="cheat-item">
<h4>🌱 Basic Command</h4>
<p><code>node -r dotenv/config app.js</code></p>
<p style="font-size: 0.85rem; margin-top: 5px;">Load dotenv first</p>
</div>
<div class="cheat-item">
<h4>📝 Long Form</h4>
<p><code>node --require dotenv/config app.js</code></p>
<p style="font-size: 0.85rem; margin-top: 5px;">Same as -r</p>
</div>
<div class="cheat-item">
<h4>🔄 Multiple Modules</h4>
<p><code>node -r mod1 -r mod2 app.js</code></p>
<p style="font-size: 0.85rem; margin-top: 5px;">Load in order</p>
</div>
<div class="cheat-item">
<h4>📦 package.json</h4>
<p><code>"start": "node -r dotenv/config app.js"</code></p>
<p style="font-size: 0.85rem; margin-top: 5px;">Add to scripts</p>
</div>
<div class="cheat-item">
<h4>🎯 Purpose</h4>
<p>Preload modules</p>
<p style="font-size: 0.85rem; margin-top: 5px;">Before main script</p>
</div>
<div class="cheat-item">
<h4>✅ Use For</h4>
<p>Config, env vars, setup</p>
<p style="font-size: 0.85rem; margin-top: 5px;">Early initialization</p>
</div>
<div class="cheat-item">
<h4>⚙️ NODE_OPTIONS</h4>
<p><code>NODE_OPTIONS='-r dotenv/config'</code></p>
<p style="font-size: 0.85rem; margin-top: 5px;">Global setting</p>
</div>
<div class="cheat-item">
<h4>💡 Benefit</h4>
<p>Clean code</p>
<p style="font-size: 0.85rem; margin-top: 5px;">No imports needed</p>
</div>
</div>
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<h2 style="font-size: 2rem; margin-bottom: 20px; color: var(--accent-pink);">🎉 Congratulations!</h2>
<p style="font-size: 1.2rem; margin-bottom: 20px;">You now understand <strong>node -r flag</strong>! 🚀</p>
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