Global Objects in Node.js

Node.js eliminates the need for explicit imports by enabling global objects to be accessed from anywhere in the application. Functionalities for managing files, streams, and processes are offered by these objects.

Node.js utilizes global as its global namespace, in contrast to browser-based JavaScript, which uses window as the global object.

Commonly Used Global Objects

Global

Access to built-in functions and objects is made possible throughout the application by the global object, which serves as the global namespace.

Example:

global.x = "Welcome to Node.js";
console.log(global.x);

Output:

Welcome to Node.js

Excessive use of global can lead to variable conflicts and maintenance challenges.

console

The console object is used for logging messages and debugging applications. It provides different methods:

• console.log() – Outputs a standard message.
• console.warn() – Displays a warning message.
• console.error() – Shows an error message.
• console.debug() – Used for debugging.

Example:

console.log("Hello");
console.warn("Warning!");
console.error("Error occurred");

Output:

Hello  
Warning!  
Error occurred  

process

The process object provides information about and control over the running Node.js process.

Example:

console.log("Process ID:", process.pid);
console.log("Node.js Version:", process.version);
console.log("Command-line arguments:", process.argv);
console.log("Process Uptime:", process.uptime(), "seconds");
console.log("Current Working Directory:", process.cwd());
console.log("Memory Usage:", process.memoryUsage());

Output (Example Data):

Process ID: 12345  
Node.js Version: v22.13.1  
Command-line arguments: [ 'C:\\Program Files\\nodejs\\node.exe' ]  
Process Uptime: 5000 seconds  
Memory Usage: { rss: 43954176, heapTotal: 7614464, heapUsed: 6585976, external: 2339203 }  

__dirname and __filename

These global variables provide information about the location of the executing script.

• __dirname – Absolute directory path of the script.
• __filename – Absolute file path of the script.

Example (test.js):

console.log("Directory Name:", __dirname);
console.log("File Name:", __filename);

Output:

Directory Name: C:\Users\Lenovo  
File Name: C:\Users\Lenovo\test.js  

Timers

setTimeout

Executes a function after a specified delay.

Example:

setTimeout(() => {
    console.log("Executed after 5 seconds");
}, 5000);

Output (after 5 seconds):

Executed after 5 seconds  

setInterval

Executes a function repeatedly at a fixed interval.

Example:

let interval = setInterval(() => {
    console.log("Runs every 3 seconds");
}, 3000);

setTimeout(() => {
    clearInterval(interval);
    console.log("Stopped");
}, 10000);

Output:

Runs every 3 seconds  
Runs every 3 seconds  
Runs every 3 seconds  
Stopped  

Buffer

In Node.js, binary data is handled using the Buffer class. Because it permits direct memory manipulation, it is beneficial for networking, file systems, and streams.

Example:

let buffer = Buffer.alloc(10);
buffer.write("Node.js");
console.log(buffer.toString());

Output:

Node.js  

Other Common Global Objects

It might be helpful:

Getting Started with Node.js: Your First Application

What’s New in Node.js 21/22? 

Best Practices for API Design in Full-Stack Development

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