let const var

`let`, `const`, and `var` are keywords used in JavaScript to declare variables.

`var` is the oldest keyword and was used to declare variables in older versions of JavaScript. However, `var` has some issues with scoping, which can lead to bugs and unexpected behavior.

`let` and `const` were introduced in ECMAScript 6 (ES6) and provide a better way to declare variables. `let` is used to declare variables that can be reassigned, while `const` is used to declare variables that cannot be reassigned.

For example:

var x = 5; // old way of declaring a variable
let y = 10; // declaring a variable with let
const z = 15; // declaring a variable with const

In general, it is recommended to use `const` for variables that do not need to be reassigned, and `let` for variables that may need to be reassigned. This can help prevent accidental changes to variables and improve code clarity.