What is a Closure?

Closures in programming languages are a method for implementing lexically scoped name binding in a language with first-class functions. Closures are also known as lexical closures or function closures. A closure is essentially a record that stores a function and its surroundings.

A closure is made of references to the state of the environment and a function that has been wrapped up (enclosed) (the lexical environment). In other words, a closure enables inner functions to access the scope of an outside function. Closures are formed whenever a function is created in JavaScript, during function creation time.