JavaScript global variables are variables that are defined outside of any function or block scope, making them accessible from anywhere within the script.

Here's a brief explanation with examples:

Global variables can be declared using the var, let, or const keywords. However, it's generally recommended to use var or let to declare global variables, as const variables are meant to be constants and shouldn't change their value.

Example 1:

var globalVariable = 10;
function myFunction() {
    console.log(globalVariable); // Accessing the global variable inside a function
}
myFunction(); // Output: 10

Example 2:

let anotherGlobalVariable = 'Hello';
function anotherFunction() {
    console.log(anotherGlobalVariable); // Accessing the global variable inside another function
}
anotherFunction(); // Output: Hello

Declaring a global variable using the window object is commonly done in the browser environment. Here's an example:

window.globalVariable = 'Hello';

By assigning a value to a property of the window object, such as globalVariable in the example above, you create a global variable that can be accessed throughout your script.

You can also use this approach to declare global variables inside a function:

function setGlobalVariable() {
  window.anotherGlobalVariable = 42;
}

setGlobalVariable();

console.log(window.anotherGlobalVariable); // Output: 42

Using window to create global variables is particularly useful in scenarios where you have multiple scripts or modules that need to share data. However, it's important to exercise caution when using global variables to avoid unintended side effects and naming conflicts.

Global variables can be accessed and modified from any part of the script, including functions, as shown in the examples above. However, it's important to use global variables judiciously, as they can make code harder to maintain and debug. It's generally recommended to limit the use of global variables and prefers local variables whenever possible.

I hope this provides you with a brief understanding of JavaScript global variables.

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