JavaScript comes with a built-in global object. When scripts create global variables using the var keyword in a web browser environment, those variables become members of the global object.
However, in Node.js, this isn’t always the case. The global object’s properties and functions vary depending on the execution context in which the script is running.
It provides a set of predefined properties and functions that are available to all JavaScript code running in a particular context, such as a web browser or Node.js environment.
In a web browser, the global object is the window object. It represents the global scope of a web page and provides access to various properties and functions, such as document, console, setTimeout, and setInterval.
console.log(globalThis === globalThis.globalThis); // true (everywhere)
console.log(window === window.window); // true (in a browser)
console.log(self === self.self); // true (in a browser or a Web Worker)
console.log(frames === frames.frames); // true (in a browser)
console.log(global === global.global); // true (in Node.js)In JavaScript, the global object always holds a reference to itself. This means that you can access the global object from within itself by using globalThis, window, self, frames, or global, depending on the execution context.
JavaScript global object example
Simple example code defines your own properties and functions on the global object by simply assigning values to it, like so:
<!DOCTYPE html>
<html>
<body>
<script>
// defining a global variable
window.myVar = 'Hello world!';
// defining a global function
function myFunc() {
console.log('Hello, world!');
}
// Call the global function from anywhere in the script
myFunc();
</script>
</body>
</html>Output:
Do comment if you have any doubts or suggestions on this JS object topic.
Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.
OS: Windows 10
Code: HTML 5 Version