## Introduction JavaScript is an object-oriented scripting language that is used to develop web applications. It has a set of keywords that are used to create, store, and manipulate variables in the code. `var`, `let` and `const` are the three keywords that are used to declare a variable in JavaScript. The main difference between `var`, `let` and `const` is their scope and the way they are used. `var` is a keyword that is used to declare a variable, which has a global scope, meaning it can be accessed from anywhere in the code. `let` is a keyword that is used to declare a variable with a block scope. It can be accessed only within the block it is declared in. `const` is a keyword that is used to declare a constant variable, which has a block scope and cannot be reassigned. In this article, we will be discussing the differences between `var`, `let` and `const` keywords in JavaScript and the best way to use them. We will also look at some of the advantages and disadvantages of using each keyword.

# Var, Let and Const Keywords in JavaScript The three keywords `var`, `let` and `const` are used in JavaScript to declare variables. The differences between them are important to understand in order to use them appropriately in your code. ## Var `Var` is the oldest keyword for declaring variables in JavaScript and was introduced in the first version of the language. Variables declared with `var` are considered to have **function scope**, meaning that they are accessible within the function in which they were declared. If a variable is declared outside of a function, it will be accessible throughout the entire program. ## Let `Let` was introduced in ES6 and is similar to `var`, but with the addition of **block scope**. Variables declared with `let` are accessible only within the block in which they were declared, for example a for loop or an if statement. ## Const `Const` was also introduced in ES6 and is used to declare **immutable** variables. This means that any variable declared with `const` cannot be reassigned or redeclared. ## Sample Code Here is an example of how each variable type can be used: ```javascript // Var var x = "Hello World!"; console.log(x); // Prints "Hello World!" // Let let y = 10; console.log(y); // Prints 10 // Const const z = true; console.log(z); // Prints true ```