How do I do closures in Emacs Lisp?

Question

I\'m trying to create a function on the fly that would return one constant value.

In JavaScript and other modern imperative languages I would use closures:

Answer 1

;; -*- lexical-binding:t -*-

(defun create-counter ()
  (let ((c 0))
    (lambda ()
      (setq c (+ c 1))
      c)))

(setq counter (create-counter))

(funcall counter) ; => 1
(funcall counter) ; => 2
(funcall counter) ; => 3 ...