Global Object in JavaScript

The Global Object in JavaScript provides built-in properties, methods, and objects that are accessible anywhere in the code.

What is the Global Object?

In browsers, the global object is called window.
In Node.js, it is called global.
In modern JavaScript (ES2020+), globalThis provides a universal way to access the global object in any environment.

Example: Accessing the Global Object

console.log(window);       // In browsers
console.log(global);       // In Node.js
console.log(globalThis);   // Works in both environments

Built-in Properties of the Global Object

Global Variables are Properties of `window`

var name = "Alice";
console.log(window.name); // Output: Alice

var declarations are added as properties of the global object, but let and const are not.

let age = 25;
console.log(window.age); // Output: undefined

Built-in Functions

The global object provides built-in functions like:

`setTimeout` and `setInterval`

setTimeout(() => console.log("Hello after 2 seconds"), 2000);
setInterval(() => console.log("Repeating every second"), 1000);

`parseInt` and `parseFloat`

console.log(parseInt("100px"));   // Output: 100
console.log(parseFloat("3.14"));  // Output: 3.14

`isNaN` (Check if Not a Number)

console.log(isNaN("hello")); // Output: true
console.log(isNaN(123));     // Output: false

Built-in Objects

The global object contains useful built-in objects:

`Math`

console.log(Math.PI);        // Output: 3.141592653589793
console.log(Math.random());  // Output: Random number between 0 and 1

`JSON` (Convert Between Objects and Strings)

const obj = { name: "Alice", age: 25 };
const jsonString = JSON.stringify(obj);
console.log(jsonString); // Output: '{"name":"Alice","age":25}'

const parsedObj = JSON.parse(jsonString);
console.log(parsedObj);  // Output: { name: 'Alice', age: 25 }

`Date`

const now = new Date();
console.log(now.toISOString()); // Output: Current date in ISO format

`globalThis` - The Universal Global Object

Before globalThis, accessing the global object in different environments was inconsistent:

Environment	Global Object
Browser	`window`
Node.js	`global`
Web Workers	`self`

Now, globalThis works everywhere:

console.log(globalThis);

🎯 Summary

✔ The Global Object contains built-in functions, objects, and properties.
✔ In browsers, it's window; in Node.js, it's global; use globalThis for a universal approach.
✔ Avoid polluting the global scope by using let and const instead of var.

🚀 The global object is powerful but should be used cautiously to avoid conflicts. Let me know if you need more details! 😊

Souy Soeng

Global Object in JavaScript