Global Scope in JavaScript

Global scope is an important concept in JavaScript. It means that a variable can be accessed from different parts of the program. When we declare a variable outside a function or block, it can usually be accessed from other parts of the program.

For example:

let name = "Abishek";

function greet() {
  console.log(name);
}

greet();
console.log(name);

Output:

Abishek
Abishek

Here, name is declared outside the function, so it can be accessed both inside and outside the function. This is called a global variable.

We can also create a global variable using const.

const country = "India";

function showCountry() {
  console.log(country);
}

showCountry();

Output:

India

The country variable is declared outside the function, so the function can access it.

Global variables can also be changed when we use let.

let score = 100;

function changeScore() {
  score = 50;
}

changeScore();
console.log(score);

Output:

50

Here, score initially has the value 100. When changeScore() is called, the value is changed to 50. This happens because score is a global variable and let allows its value to be reassigned.

But if we use const, the value cannot be reassigned.

const score = 100;
score = 50;

Output:

TypeError: Assignment to constant variable.

Global variables are useful when the same value needs to be used in different parts of a program. However, using too many global variables is not recommended because they can be accidentally changed and may cause bugs.

In simple words, global scope means a variable can be accessed from different parts of a JavaScript program. We should use global variables carefully and use local variables whenever possible.