📤 Node.js – Console & Process – Master Output, Logging, and System Controls in Node.js

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🧲 Introduction – What Are console and process in Node.js?

In Node.js, console and process are powerful built-in global objects. They allow you to interact with the terminal, log output, track errors, and access detailed runtime information.

• console provides standard output, warnings, and debugging messages.
• process gives access to system-level data like memory usage, environment variables, and CLI arguments.

🎯 In this guide, you’ll learn:

• How to use console methods for effective logging
• How process helps manage the Node.js runtime
• Real examples of debugging, input/output, and scripting
• Best practices for using both in your applications

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🖨️ Node.js console Object – Logging and Debugging

The console object lets you output messages, debug info, errors, and inspect objects directly in the terminal.

✅ Common console Methods

Method	Description
console.log()	Logs standard output
console.error()	Logs error messages (stderr)
console.warn()	Logs warning messages
console.info()	Alias for console.log()
console.dir()	Logs an object in JSON-like format
console.table()	Displays tabular data
console.time() / console.timeEnd()	Measures execution time between the calls

🧪 Example:

console.log("Hello from Node.js!");
console.error("This is an error!");
console.table([{ id: 1 }, { id: 2 }]);

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⚙️ Node.js process Object – Runtime and System Control

The process object is a global Node.js object that provides information about the currently running process.

✅ Useful process Properties & Methods

Property / Method	Description
process.argv	Array of command-line arguments
process.env	Environment variables
process.exit([code])	Exit the current process
process.cwd()	Returns current working directory
process.memoryUsage()	Memory stats of Node.js process
process.uptime()	Time (in seconds) the process has been running

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🧪 Examples – Console + Process in Action

Print CLI arguments:

console.log(process.argv);
// Output: ['node', 'app.js', 'arg1', 'arg2']

Access environment variable:

console.log(process.env.NODE_ENV);  // production or development

Exit process manually:

if (!process.env.API_KEY) {
  console.error("Missing API_KEY. Exiting...");
  process.exit(1);
}

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🧰 Combining console and process for Real Applications

Sample Script with Logging + Env + Exit:

console.log("App Started");

if (!process.env.USER) {
  console.warn("No user detected in environment.");
}

console.time("loop");
for (let i = 0; i < 1e6; i++) {}  // Simulated task
console.timeEnd("loop");

console.log("Memory Usage:", process.memoryUsage());
console.log("App finished.");

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📌 Summary – Recap & Next Steps

The console and process objects are essential tools for every Node.js developer. Whether you’re logging events, handling configuration, or measuring performance, these tools make it easy to interact with the terminal and system environment.

🔍 Key Takeaways:

• console.log(), error(), table(), and time() are great for output and debugging
• process gives access to CLI args, memory, uptime, and env vars
• Use process.exit() responsibly for flow control

⚙️ Real-world relevance:
Used in CLI tools, logging systems, config scripts, and automated tasks across all Node.js projects.

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❓FAQs – Node.js Console & Process

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❓ What is the difference between console.log() and console.error()?
✅ console.log() writes to stdout, while console.error() writes to stderr. This allows better error handling in logs.

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❓ How can I pass arguments to a Node.js script?
✅ Use the command line:

node app.js arg1 arg2

Access them via process.argv[2], process.argv[3], etc.

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❓ How do I access environment variables in Node.js?
✅ Use:

process.env.VARIABLE_NAME

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❓ Can I use console.table() in Node.js like in browsers?
✅ Yes! It works exactly the same in the terminal.

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❓ When should I use process.exit()?
✅ Use it when you need to end the app early due to errors or conditions not being met (e.g., missing config).

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