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Javascript Module Pattern

/ Published in: JavaScript
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The module pattern was originally defined as a way to provide both private and public encapsulation for classes in conventional software engineering.
In JavaScript, the module pattern is used to further emulate the concept of classes in such a way that we're able to include both public/private methods and variables inside a single object, thus shielding particular parts from the global scope. What this results in is a reduction in the likelihood of your function names conflicting with other functions defined in additional scripts on the page.

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  1. var basketModule = (function () {
  2.   var basket = []; //private
  3.   function doSomethingPrivate() {
  4.     //...
  5.   }
  6.   function doSomethingElsePrivate() {
  7.     //...
  8.   }
  9.   return { //exposed to public
  10.     addItem: function (values) {
  11.       basket.push(values);
  12.     },
  13.     getItemCount: function () {
  14.       return basket.length;
  15.     },
  16.     doSomething: doSomethingPrivate(),
  17.     getTotal: function () {
  18.       var q = this.getItemCount(),
  19.         p = 0;
  20.       while (q--) {
  21.         p += basket[q].price;
  22.       }
  23.       return p;
  24.     }
  25.   }
  26. }());
  27.  
  28.  
  29. // basketModule is an object with properties which can also be methods
  30. basketModule.addItem({
  31.   item: 'bread',
  32.   price: 0.5
  33. });
  34. basketModule.addItem({
  35.   item: 'butter',
  36.   price: 0.3
  37. });
  38. console.log(basketModule.getItemCount());
  39. console.log(basketModule.getTotal());
  40. // however, the following will not work:
  41. console.log(basketModule.basket); // (undefined as not inside the returned object)
  42. console.log(basket); //(only exists within the scope of the closure)

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