Which keyword is not applicable when declaring a variable in JavaScript?

In JavaScript, the keywords used to declare variables include 'let', 'const', and 'var'. Each of these keywords serves a specific purpose in terms of the variable's scope and mutability.

• 'let' allows you to declare variables that can be reassigned, with block scope, meaning they are only accessible within the block they are defined.

• 'const' is used for declaring variables that are constant and cannot be reassigned after their initial assignment. It also has block scope.

• 'var', on the other hand, is an older keyword used to declare variables that can be reassigned and have function scope or global scope, depending on where they are declared.

In contrast, the keyword 'set' does not serve as a variable declaration keyword in JavaScript. Instead, it is often associated with the creation of setter methods in object-oriented programming, which are used to control how properties of an object are set.

Therefore, the keyword that does not apply when declaring a variable in JavaScript is 'set'.