module.js

// here's a module with public and private members using the constructor pattern
// see here: http://javascript.crockford.com/private.html

var A_Module = function () {
  // this hello function is public
  public_api = { hello: function () { return "hello" } }
  
  // this function is private
  function times(a, b) { return a * b }
  
  // this function is public
  // this is the same as if we'd put this definition within the public_api object above (like `hello` is)
  public_api.square = function (a) { return times(a, a) }
  
  return public_api
}

// here's how we'd use that module.

// first construct it:
let the_module = new A_Module()

the_module.square(5) // 25
the_module.hello() // "hello"

the_module.times // undefined




// here's an equivalent module using the revealing module pattern with es6 features
// this is what Crockford does these days

function another_module() {
  times = function (a, b) {
    return a * b
  }
  
  square = function (a) {
    return times(a, a)
  }
  
  hello = function () {
    return "hello"
  }

  return Object.freeze({
      square, hello
  })
}

// and here's how we'd use it

// this time we *don't* need the `new` keyword
let the_module = another_module()

the_module.square(5) // 25
the_module.hello() // "hello"

the_module.times // undefinedthe_module

use-it.js

// let's try the second example