🧭 Node.js – Command Line Options – Master Node.js CLI Flags for Efficient Development

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🧲 Introduction – Why Learn Node.js Command Line Options?

Node.js provides a rich set of command line options (CLI flags) that give you more control over how Node executes JavaScript code. These flags allow developers to enable debugging, run code snippets, measure performance, set environment variables, and customize the Node.js runtime behavior.

Understanding these options helps you become a more efficient and powerful Node.js developer, especially when working with tools, scripts, or in DevOps environments.

🎯 In this guide, you’ll learn:

• How to use Node.js command line options
• The most commonly used CLI flags
• Practical examples of command usage
• Debugging, scripting, and environment control via CLI

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⚙️ How to Use Node.js Command Line Options

To view all available CLI options, use:

node --help

🧪 Output:
You’ll get a long list of flags like --inspect, --trace-warnings, --eval, --version, etc.

To use a flag, simply type:

node [option] [script.js]

Or run inline code like:

node -e "console.log('Hello from Node CLI')"

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📘 Commonly Used Node.js CLI Flags

Here’s a table of the most helpful Node.js CLI options with examples:

🏷️ Option	📘 Description	💻 Example
-v or --version	Displays Node.js version	node -v
-e	Executes inline JavaScript	node -e "console.log(5 + 5)"
-p	Prints result of the expression	node -p "3 * 7"
--inspect	Enables Chrome DevTools debugger	node --inspect app.js
--inspect-brk	Breaks before first line for debugging	node --inspect-brk app.js
--trace-warnings	Displays warnings with stack traces	node --trace-warnings app.js
--experimental-modules	Enables experimental ES module support	node --experimental-modules app.mjs
--require	Preloads modules before execution	node --require dotenv/config app.js
--trace-deprecation	Logs use of deprecated features	node --trace-deprecation app.js

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🧪 Examples – Running Node.js Commands with Flags

✅ Print Output Directly

node -p "10 * 10"

Output:

100

✅ Debug with Chrome DevTools

node --inspect-brk server.js

Then open chrome://inspect in your browser to start debugging.

✅ Execute Inline JavaScript

node -e "console.log('Inline code run successfully!')"

Output:

Inline code run successfully!

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🛠️ Advanced Node.js Flags

⚙️ Option	🔍 Use Case
--max-old-space-size=SIZE	Set memory limit in MB (useful for heavy apps)
--trace-gc	Logs garbage collection activity
--abort-on-uncaught-exception	Crash app on uncaught exceptions (for diagnostics)
--es-module-specifier-resolution=node	Customize ES module path resolution behavior

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🔐 Node.js Environment Variable Flags

Node.js supports setting environment variables inline:

NODE_ENV=production node app.js   # UNIX

On Windows (CMD):

set NODE_ENV=production && node app.js

Or PowerShell:

$env:NODE_ENV="production"; node app.js

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🧰 Best Practices Using Node CLI Options

✅ Practice	💡 Tip
Use --inspect for debugging	Combine with DevTools or VS Code breakpoints
Use -e/-p for quick tests	Avoid creating files for one-liners or quick math
Log deprecations & warnings	Use --trace-deprecation and --trace-warnings
Profile memory & performance	Use --trace-gc and --max-old-space-size
Automate with CLI scripts	Use in npm run scripts and CI/CD pipelines

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📌 Summary – Recap & Next Steps

Node.js CLI options are powerful tools that can boost your development, debugging, and deployment efficiency. From running inline code to inspecting memory leaks, mastering these flags will help you unlock Node.js’s full capabilities.

🔍 Key Takeaways:

• CLI options let you control how Node.js executes code
• Use flags like --inspect, -e, -p, and --trace-warnings regularly
• Useful in automation scripts, debugging, and quick experimentation

⚙️ Real-world relevance:
Used in production setups, testing workflows, deployment scripts, and debugging environments.

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❓FAQs – Node.js Command Line Options

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❓ How do I see all Node.js CLI options?
✅ Run:

node --help

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❓ What’s the difference between -e and -p?
✅ -e executes JavaScript; -p evaluates and prints the result automatically.

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❓ How can I debug Node.js apps with Chrome?
✅ Use:

node --inspect-brk app.js

Then open chrome://inspect.

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❓ Can I preload modules before app execution?
✅ Yes. Use --require flag:

node --require dotenv/config app.js

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