Closures: why are they so useful?

Question

As an OO developer, maybe I have difficulty seeing its value. What added value do they give? Do they fit in an OO world?

Answer 1

Maybe in the world of compiled programming the benefits of closures are less noticeable. In JavaScript closures are incredibly powerful. This is for two reasons:

1) JavaScript is an interpreted language, so instruction efficiency and namespace conservation are incredibly important for faster and more responsive execution from large programs or programs that evaluate large amounts of input.

2) JavaScript is a lambda language. This means in JavaScript functions are first class objects that define scope and scope from a parent function is accessible to child objects. This is important since a variable can be declared in a parent function, used in a child function, and retain value even after the child function returns. That means a variable can be reused by a function many times with a value already defined by the last iteration of that function.

As a result closures are incredibly powerful and provide superior efficiency in JavaScript.