Run Node.js with zero-turnaround using watch mode
📦 Node.js-> Command Line
✨ The Prompt Phrase
node --watch app.js
💻 Code Preview
📦 All-in-One Code
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Run Node.js with zero-turnaround using watch mode - 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;
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--text-secondary: #94a3b8;
--gradient-watch: linear-gradient(135deg, #84cc16 0%, #10b981 100%);
--gradient-reload: linear-gradient(135deg, #10b981 0%, #059669 100%);
--shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
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* {
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body {
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color: var(--text-primary);
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.container {
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.progress-container {
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.progress-bar {
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.watch-icon {
font-size: 5rem;
margin-bottom: 20px;
animation: watchPulse 2s ease-in-out infinite;
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@keyframes watchPulse {
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.section {
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.section-title {
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.copy-btn:hover {
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pre {
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.step h3 {
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.feature-icon {
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font-size: 1.3rem;
}
.demo-container {
background: var(--bg-secondary);
border-radius: 20px;
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}
.watch-demo {
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.demo-box {
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.reload-indicator {
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color: white;
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font-size: 0.8rem;
animation: blink 1s ease-in-out infinite;
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@keyframes blink {
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.terminal {
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border-left: 4px solid var(--accent-red);
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.cheat-sheet {
background: var(--gradient-watch);
border-radius: 20px;
padding: 40px;
margin: 30px 0;
color: white;
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padding: 20px;
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.cheat-item h4 {
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font-size: 0.9rem;
color: white;
}
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}
.footer {
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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-watch);
border-radius: 20px;
font-size: 0.85rem;
font-weight: 600;
margin: 5px;
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.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: 1rem; 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; }
.watch-demo { 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="watch-icon">👁️</div>
<h1>Master Node Watch Mode!</h1>
<div class="command-display">node --watch app.js</div>
<p>Auto-reload on file changes! 🔄</p>
</div>
</div>
<div class="container">
<!-- What Is It -->
<section class="section">
<h2 class="section-title">🤔 What Is Watch Mode?</h2>
<div class="card">
<p style="font-size: 1.2rem; margin-bottom: 20px;">
<code>node --watch</code> is a <span class="highlight">built-in Node.js feature</span> that automatically restarts your application whenever you save changes to your files - no need for external tools like nodemon! 👁️
</p>
<p style="margin-bottom: 20px;">
Think of it like having a personal assistant watching your code! 🤖 Every time you save a file, Node automatically restarts your app with the new changes. No more manually stopping and restarting - it's instant, built-in, and zero configuration!
</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-watch">--watch</code> - Enable watch mode</li>
<li><code>app.js</code> - Your entry file</li>
<li>Monitors file changes automatically</li>
<li>Restarts on save (zero turnaround!)</li>
</ul>
</div>
<div style="margin-top: 30px;">
<h3 style="color: var(--accent-pink); margin-bottom: 15px;">What's Zero Turnaround? 🔍</h3>
<p>Zero turnaround means <strong>instant feedback</strong> - the time between saving your code and seeing the results is nearly zero! No manual restarts, no waiting. Save → Auto-reload → See changes immediately!</p>
</div>
<div class="warning" style="margin-top: 20px;">
<strong>Node Version Required:</strong> Watch mode requires Node.js 18.11.0 or higher (stable in Node 19+)
</div>
</div>
</section>
<!-- Visual Demo -->
<section class="section">
<h2 class="section-title">📊 How It Works Visually</h2>
<div class="card">
<h3 style="margin-bottom: 20px; text-align: center;">The Watch Cycle! 🔄</h3>
<div class="watch-demo">
<div class="demo-box">
<div style="font-size: 3rem; margin-bottom: 10px;">💾</div>
<h4 style="color: var(--accent-lime);">1. Save File</h4>
<p style="color: var(--text-secondary); font-size: 0.9rem;">Edit & save code</p>
</div>
<div style="font-size: 2rem; color: var(--accent-lime);">→</div>
<div class="demo-box">
<div class="reload-indicator">Watching!</div>
<div style="font-size: 3rem; margin-bottom: 10px;">👁️</div>
<h4 style="color: var(--accent-lime);">2. Detect Change</h4>
<p style="color: var(--text-secondary); font-size: 0.9rem;">Node sees update</p>
</div>
<div style="font-size: 2rem; color: var(--accent-lime);">→</div>
<div class="demo-box">
<div style="font-size: 3rem; margin-bottom: 10px;">🔄</div>
<h4 style="color: var(--accent-lime);">3. Auto Restart</h4>
<p style="color: var(--text-secondary); font-size: 0.9rem;">Instant reload!</p>
</div>
</div>
<div class="success" style="margin-top: 30px;">
<strong>Result:</strong> Instant feedback loop - save and see changes immediately!
</div>
</div>
</section>
<!-- Why Use It -->
<section class="section">
<h2 class="section-title">✨ Why Use Watch Mode?</h2>
<div class="card">
<div class="feature-grid">
<div class="feature-card">
<div class="feature-icon">⚡</div>
<div class="feature-title">Instant Reload</div>
<p style="color: var(--text-secondary);">See changes immediately!</p>
</div>
<div class="feature-card">
<div class="feature-icon">🎯</div>
<div class="feature-title">Built-in</div>
<p style="color: var(--text-secondary);">No nodemon needed!</p>
</div>
<div class="feature-card">
<div class="feature-icon">🚀</div>
<div class="feature-title">Zero Config</div>
<p style="color: var(--text-secondary);">Works out of the box!</p>
</div>
<div class="feature-card">
<div class="feature-icon">💪</div>
<div class="feature-title">Productivity</div>
<p style="color: var(--text-secondary);">Focus on coding!</p>
</div>
<div class="feature-card">
<div class="feature-icon">🔄</div>
<div class="feature-title">Auto Restart</div>
<p style="color: var(--text-secondary);">Hands-free!</p>
</div>
<div class="feature-card">
<div class="feature-icon">🎨</div>
<div class="feature-title">Better DX</div>
<p style="color: var(--text-secondary);">Developer experience!</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: Start Watch Mode</h3>
<p>Run <code>node --watch app.js</code> to start your app in watch mode.</p>
</div>
<div class="step">
<h3>Step 2: Monitor Files</h3>
<p>Node watches your entry file and all its dependencies.</p>
</div>
<div class="step">
<h3>Step 3: Detect Changes</h3>
<p>When you save any watched file, Node detects the change.</p>
</div>
<div class="step">
<h3>Step 4: Graceful Shutdown</h3>
<p>Node stops the current process cleanly.</p>
</div>
<div class="step">
<h3>Step 5: Restart Application</h3>
<p>Node immediately restarts with the new code.</p>
</div>
<div class="step">
<h3>Step 6: Continue Watching</h3>
<p>Process repeats - watch, detect, restart! 🎉</p>
</div>
</div>
</div>
</section>
<!-- Live Demo -->
<section class="section">
<h2 class="section-title">🎮 Interactive Demo</h2>
<div class="demo-container">
<div style="margin-bottom: 30px; text-align: center;">
<h4 style="margin-bottom: 15px;">See Watch Mode in Action! 👁️</h4>
<button class="demo-button" onclick="simulateWatch()">
<span>👁️</span>
<span>Start Watch Mode</span>
</button>
<button class="demo-button" onclick="simulateChange()">
<span>💾</span>
<span>Save File Change</span>
</button>
<button class="demo-button" onclick="simulateMultiple()">
<span>🔄</span>
<span>Multiple Changes</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 watch files...</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('options')">Options</button>
<button class="tab" onclick="switchTab('patterns')">Watch Patterns</button>
<button class="tab" onclick="switchTab('comparison')">vs nodemon</button>
</div>
<div id="basic" class="tab-content active">
<h3 style="color: var(--accent-pink); margin-bottom: 15px;">Basic Watch Mode</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"># Basic watch mode</span>
node --watch app.js
<span class="code-comment"># Watch with arguments</span>
node --watch server.js --port=3000
<span class="code-comment"># Watch with environment variables</span>
NODE_ENV=development node --watch app.js
<span class="code-comment"># What happens:</span>
<span class="code-comment"># 1. App starts</span>
<span class="code-comment"># 2. Node watches files</span>
<span class="code-comment"># 3. On save → auto restart</span>
<span class="code-comment"># 4. Repeat forever!</span>
<span class="code-comment"># Stop watching: Ctrl+C</span></code></pre>
</div>
<div class="success" style="margin-top: 15px;">
<strong>Result:</strong> Instant auto-reload on every save!
</div>
</div>
<div id="options" class="tab-content">
<h3 style="color: var(--accent-pink); margin-bottom: 15px;">Watch Mode Options</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('options-code')">📋 Copy</button>
</div>
<pre><code id="options-code"><span class="code-comment"># Watch specific files/patterns</span>
node --watch-path=./src --watch-path=./lib app.js
<span class="code-comment"># Watch with preserve output (Node 20+)</span>
node --watch --watch-preserve-output app.js
<span class="code-comment"># Combine with other flags</span>
node --watch --inspect app.js <span class="code-comment"># With debugger</span>
node --watch --experimental-modules app.mjs
<span class="code-comment"># In package.json scripts:</span>
{
<span class="code-string">"scripts"</span>: {
<span class="code-string">"dev"</span>: <span class="code-string">"node --watch app.js"</span>,
<span class="code-string">"dev:inspect"</span>: <span class="code-string">"node --watch --inspect app.js"</span>
}
}
<span class="code-comment"># Then run:</span>
npm run dev</code></pre>
</div>
<div class="tip" style="margin-top: 15px;">
<strong>Pro Tip:</strong> Use package.json scripts for easier command management!
</div>
</div>
<div id="patterns" class="tab-content">
<h3 style="color: var(--accent-pink); margin-bottom: 15px;">Watch Specific Patterns</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>
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</div>
<button class="copy-btn" onclick="copyCode('patterns-code')">📋 Copy</button>
</div>
<pre><code id="patterns-code"><span class="code-comment"># Watch specific directory</span>
node --watch-path=./src app.js
<span class="code-comment"># Watch multiple directories</span>
node --watch-path=./src --watch-path=./config app.js
<span class="code-comment"># By default, watches:</span>
<span class="code-comment"># - Entry file (app.js)</span>
<span class="code-comment"># - All required/imported files</span>
<span class="code-comment"># - Dependencies recursively</span>
<span class="code-comment"># Does NOT watch:</span>
<span class="code-comment"># - node_modules (by default)</span>
<span class="code-comment"># - .git directory</span>
<span class="code-comment"># - Hidden files (unless specified)</span>
<span class="code-comment"># Example project structure:</span>
<span class="code-comment"># /project</span>
<span class="code-comment"># /src</span>
<span class="code-comment"># app.js ← Watched</span>
<span class="code-comment"># utils.js ← Watched (imported by app.js)</span>
<span class="code-comment"># /node_modules ← NOT watched</span>
<span class="code-comment"># package.json ← NOT watched (unless specified)</span></code></pre>
</div>
</div>
<div id="comparison" class="tab-content">
<h3 style="color: var(--accent-pink); margin-bottom: 15px;">Watch Mode vs nodemon</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>
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</div>
<button class="copy-btn" onclick="copyCode('comparison-code')">📋 Copy</button>
</div>
<pre><code id="comparison-code"><span class="code-comment"># Node --watch (built-in)</span>
node --watch app.js
<span class="code-comment">✅ No installation needed</span>
<span class="code-comment">✅ Zero configuration</span>
<span class="code-comment">✅ Official Node.js feature</span>
<span class="code-comment">✅ Fast and lightweight</span>
<span class="code-comment">❌ Fewer customization options</span>
<span class="code-comment">❌ Requires Node 18.11+</span>
<span class="code-comment"># nodemon (external tool)</span>
nodemon app.js
<span class="code-comment">✅ More configuration options</span>
<span class="code-comment">✅ Works with older Node versions</span>
<span class="code-comment">✅ Can run non-Node scripts</span>
<span class="code-comment">✅ More watch patterns</span>
<span class="code-comment">❌ Requires npm install</span>
<span class="code-comment">❌ External dependency</span>
<span class="code-comment"># When to use --watch:</span>
<span class="code-comment"># - Simple Node.js apps</span>
<span class="code-comment"># - No external dependencies preferred</span>
<span class="code-comment"># - Node 18+ available</span>
<span class="code-comment"># When to use nodemon:</span>
<span class="code-comment"># - Complex watch patterns needed</span>
<span class="code-comment"># - Older Node versions</span>
<span class="code-comment"># - Need advanced features</span></code></pre>
</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 with Old Node Versions</strong></span>
<span class="accordion-icon">▼</span>
</div>
<div class="accordion-content">
<div class="accordion-body">
<div class="warning">
<strong>Problem:</strong> --watch doesn't work on Node versions below 18.11
</div>
<div class="success" style="margin-top: 15px;">
<strong>Solution:</strong> Upgrade to Node 18.11+ or use nodemon for older versions!
</div>
</div>
</div>
</div>
<div class="accordion-item">
<div class="accordion-header" onclick="toggleAccordion(this)">
<span><strong>2. Expecting node_modules to Be Watched</strong></span>
<span class="accordion-icon">▼</span>
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<div class="accordion-content">
<div class="accordion-body">
<div class="warning">
<strong>Problem:</strong> Changes in node_modules don't trigger restart
</div>
<div class="success" style="margin-top: 15px;">
<strong>Solution:</strong> This is intentional - node_modules is ignored by default!
</div>
</div>
</div>
</div>
<div class="accordion-item">
<div class="accordion-header" onclick="toggleAccordion(this)">
<span><strong>3. Not Handling Cleanup</strong></span>
<span class="accordion-icon">▼</span>
</div>
<div class="accordion-content">
<div class="accordion-body">
<div class="warning">
<strong>Problem:</strong> Resources not cleaned up before restart (open connections, timers)
</div>
<div class="success" style="margin-top: 15px;">
<strong>Solution:</strong> Add proper cleanup in process exit handlers!
</div>
</div>
</div>
</div>
<div class="accordion-item">
<div class="accordion-header" onclick="toggleAccordion(this)">
<span><strong>4. Watching Too Many Files</strong></span>
<span class="accordion-icon">▼</span>
</div>
<div class="accordion-content">
<div class="accordion-body">
<div class="warning">
<strong>Problem:</strong> Performance issues from watching large directories
</div>
<div class="success" style="margin-top: 15px;">
<strong>Solution:</strong> Use --watch-path to specify only needed directories!
</div>
</div>
</div>
</div>
</div>
</div>
</section>
<!-- Pro Tips -->
<section class="section">
<h2 class="section-title">🚀 Pro Tips</h2>
<div class="card">
<div class="tip">
<strong>Use in package.json</strong> - Add <code>"dev": "node --watch app.js"</code> to scripts!
</div>
<div class="tip">
<strong>Combine with debugger</strong> - Use <code>--watch --inspect</code> for debugging!
</div>
<div class="tip">
<strong>Graceful shutdown</strong> - Handle SIGTERM/SIGINT for proper cleanup!
</div>
<div class="tip">
<strong>Watch specific paths</strong> - Use <code>--watch-path</code> for better performance!
</div>
<div class="tip">
<strong>Environment variables</strong> - Set NODE_ENV=development for dev mode!
</div>
<div class="tip">
<strong>Preserve output</strong> - Use <code>--watch-preserve-output</code> to keep logs visible!
</div>
<div class="tip">
<strong>Testing</strong> - Great for TDD - watch test files and see results instantly!
</div>
</div>
</section>
<!-- Quiz -->
<section class="section">
<h2 class="section-title">🎯 Knowledge Check Quiz</h2>
<div class="quiz-container">
<p style="margin-bottom: 30px; font-size: 1.1rem;">Test your understanding! 🧠</p>
<div class="quiz-question">
<h3>Question 1: What does --watch do?</h3>
<div class="quiz-options">
<div class="quiz-option" onclick="checkAnswer(this, false, 1)">A) Monitors CPU usage</div>
<div class="quiz-option" onclick="checkAnswer(this, true, 1)">B) Auto-restarts on file changes</div>
<div class="quiz-option" onclick="checkAnswer(this, false, 1)">C) Logs all file access</div>
</div>
<div class="quiz-feedback" id="feedback1"></div>
</div>
<div class="quiz-question">
<h3>Question 2: What Node version is required?</h3>
<div class="quiz-options">
<div class="quiz-option" onclick="checkAnswer(this, false, 2)">A) Node 14+</div>
<div class="quiz-option" onclick="checkAnswer(this, true, 2)">B) Node 18.11+</div>
<div class="quiz-option" onclick="checkAnswer(this, false, 2)">C) Any Node version</div>
</div>
<div class="quiz-feedback" id="feedback2"></div>
</div>
<div class="quiz-question">
<h3>Question 3: What is NOT watched by default?</h3>
<div class="quiz-options">
<div class="quiz-option" onclick="checkAnswer(this, false, 3)">A) Entry file</div>
<div class="quiz-option" onclick="checkAnswer(this, true, 3)">B) node_modules directory</div>
<div class="quiz-option" onclick="checkAnswer(this, false, 3)">C) Imported files</div>
</div>
<div class="quiz-feedback" id="feedback3"></div>
</div>
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<h3 style="color: var(--accent-green); font-size: 1.5rem;">🎉 Quiz Complete!</h3>
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</section>
<!-- Summary Card -->
<section class="section">
<h2 class="section-title">📚 Quick Reference</h2>
<div class="cheat-sheet">
<h3 style="margin-bottom: 20px; font-size: 2rem;">Watch Mode Cheat Sheet! 🔖</h3>
<div class="cheat-grid">
<div class="cheat-item">
<h4>👁️ Basic Command</h4>
<p><code>node --watch app.js</code></p>
<p style="font-size: 0.85rem; margin-top: 5px;">Start watch mode</p>
</div>
<div class="cheat-item">
<h4>📁 Watch Path</h4>
<p><code>--watch-path=./src</code></p>
<p style="font-size: 0.85rem; margin-top: 5px;">Specific directory</p>
</div>
<div class="cheat-item">
<h4>🔍 With Debugger</h4>
<p><code>--watch --inspect</code></p>
<p style="font-size: 0.85rem; margin-top: 5px;">Debug mode</p>
</div>
<div class="cheat-item">
<h4>📦 Package.json</h4>
<p><code>"dev": "node --watch"</code></p>
<p style="font-size: 0.85rem; margin-top: 5px;">npm script</p>
</div>
<div class="cheat-item">
<h4>⚡ Purpose</h4>
<p>Auto-reload on save</p>
<p style="font-size: 0.85rem; margin-top: 5px;">Zero turnaround</p>
</div>
<div class="cheat-item">
<h4>✅ Requirements</h4>
<p>Node 18.11+</p>
<p style="font-size: 0.85rem; margin-top: 5px;">Built-in feature</p>
</div>
<div class="cheat-item">
<h4>🚫 Not Watched</h4>
<p>node_modules, .git</p>
<p style="font-size: 0.85rem; margin-top: 5px;">By default</p>
</div>
<div class="cheat-item">
<h4>🛑 Stop</h4>
<p>Ctrl+C</p>
<p style="font-size: 0.85rem; margin-top: 5px;">Exit watch mode</p>
</div>
</div>
</div>
</section>
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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.js Watch Mode</strong>! 🚀</p>
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<span class="badge">👁️ Watch Master</span>
<span class="badge">⚡ Auto-Reload Pro</span>
<span class="badge">🚀 Node.js Expert</span>
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<p style="color: var(--text-secondary); font-size: 0.9rem;">Made with ❤️ for developers learning Node.js</p>
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