Scope of variable in JavaScript with example.

In JavaScript, variables have a scope that determines where they are available for use in your code. There are two types of variable scope in JavaScript: global scope and local scope.

Global scope refers to the availability of a variable throughout your entire code. When you declare a variable outside of any function, it is considered to be in global scope. This means that it can be accessed and modified from anywhere in your code.

Here is an example of a variable in global scope:

let globalVariable = 'Hello, World!';

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

greet(); // Output: 'Hello, World!'

Local scope refers to the availability of a variable within a specific function. When you declare a variable inside a function, it is considered to be in local scope and can only be accessed and modified within that function.

Here is an example of a variable in local scope:

function greet() {
  let localVariable = 'Hello, World!';
  console.log(localVariable);
}

greet(); // Output: 'Hello, World!'
console.log(localVariable); // Uncaught ReferenceError: localVariable is not defined

It's important to note that variables in JavaScript are function-scoped, rather than block-scoped like in some other programming languages. This means that variables declared within a block of code (e.g. within an if statement or a for loop) are still considered to be in the local scope and are only available within the function in which they are defined.

Here is an example of how variables are function-scoped in JavaScript:

function greet() {
  if (true) {
    let localVariable = 'Hello, World!';
  }
  console.log(localVariable); // Uncaught ReferenceError: localVariable is not defined
}

greet();

In contrast, variables declared with the const or let keywords within a block of code are block-scoped and are only available within that block of code.

It's important to understand the concept of variable scope in JavaScript, as it can affect the way your code runs and can lead to errors if you try to access or modify a variable that is not in the correct scope.

I hope this helps to clarify the concept of variable scope in JavaScript! Let me know if you have any questions or need further explanation.