Global Variables in JavaScript: Understanding and Best Practices

In JavaScript, global variables are variables that are accessible from any part of your code, regardless of where they are declared. However, working with global variables can lead to unintended consequences, especially when the scope and lifetimes of variables are not carefully managed. This article explores the concept of global variables, their uses, risks, and best practices.

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What Are Global Variables?

A global variable is a variable that is defined outside of any function or block scope. This makes it accessible throughout the entire program, including functions, objects, or other code blocks.

Example:

let globalVar = 'I am a global variable';

function showGlobal() {
  console.log(globalVar);  // Accessible inside functions
}

showGlobal();  // Output: "I am a global variable"
console.log(globalVar);  // Output: "I am a global variable"

In the example above, globalVar is declared in the global scope, meaning it can be accessed anywhere in the program.

How Do Global Variables Get Created?