Super Simple Tutorial on How to Create a Functor in JavaScript

functor.js

// Here is a quick tutorial on how to create a functor, an object that acts
// both as function and an object of functions (e.g. much like jQuery's globally 
// available $ object)

// This is a factory method that creates the functor for us:
function createFunctor() {
  
  // Declared variables are scoped within the createFunctor function
  // so they are practically private:
  var name = 'World';

  // The functor is just an ordinary function, and is fairly simple to create:
  var functor = function() {
    console.log('Hello ' + name);
  };
  
  // The functor is also a Javascript Object, meaning you can attach functions
  // to it like this:
  functor.setName = function(newName) {
    name = newName;
  };
  
  // Return the functor
  return functor;
  
}

testcase.js

// Test case:
var $ = createFunctor();

$();
// outputs 'Hello World'

$.setName('Magic Mike');
$();
// outputs 'Hello Magic Mike'