Interface Fiddle

This defines the interface Fiddle

by Abid Akhtar

JavaScript

// Constructor.
var Interface = function(name, methods) {
  if (arguments.length != 2) {
    throw new Error("Interface constructor called with " + arguments.length +
      "arguments, but expected exactly 2.");
  }
  this.name = name;
  this.methods = [];
  for (var i = 0, len = methods.length; i < len; i++) {
    if (typeof methods[i] !== 'string') {
      throw new Error("Interface constructor expects method names to be " + "passed in as a string.");
    }
    this.methods.push(methods[i]);
  }
};
// Static class method.
Interface.ensureImplements = function(object) {
  if (arguments.length < 2) {
    throw new Error("Function Interface.ensureImplements called with " +
      arguments.length + "arguments, but expected at least 2.");
  }
  for (var i = 1, len = arguments.length; i < len; i++) {
    var interface = arguments[i];
    if (interface.constructor !== Interface) {
      throw new Error("Function Interface.ensureImplements expects arguments" + "two and above to be instances of Interface.");
    }
    for (var j = 0, methodsLen = interface.methods.length; j < methodsLen; j++) {
      var method = interface.methods[j];
      if (!object[method] || typeof object[method] !== 'function') {
        throw new Error("Function Interface.ensureImplements: object " + "does not implement the " + interface.name + " interface. Method " + method + " was not found.");
      }
    }
  }
};

var Publication = new Interface('Publication', ['getIsbn', 'setIsbn', 'getTitle',
  'setTitle', 'getAuthor', 'setAuthor', 'display'
]);
var Book = function(isbn, title, author) { // implements Publication
  this.setIsbn(isbn);
  this.setTitle(title);
  this.setAuthor(author);
}
Book.prototype = {
  checkIsbn: function(isbn) {
    if (isbn == undefined || typeof isbn != 'string') {
      return false;
    }
    isbn = isbn.replace(/-/.
      ''); // Remove dashes.
    if (isbn.length != 10 && isbn.length != 13) {
      return false;
    }
    var sum = 0;
    if (isbn.length === 10)...