Defining a constructor and it's prototype methods all in a single call.

class-def.js

// This is a fairly common pattern. First, define a constructor...
var Person = function(firstName, lastName) {
  this.firstName = firstName;
  this.lastName = lastName;
};

// ...then define some methods by mixing into the prototype
$.extend(Person.prototype, {
  sayHello: function() {
    console.log('Hello, I\'m ' + this.getFullName());
  },
  getFullName: function() {
    return this.firstName + ' ' + this.lastName;
  }
});

// Example use:
var person = new Person('Keegan', 'Watkins');
person.sayHello(); // logs "Hello, I'm Keegan Watkins"

// As a shorthand though, we can define the constructor AND
// the prototype methods in a single call, like this:
var Person2 = $.extend(function(firstName, lastName) {
  this.firstName = firstName;
  this.lastName = lastName;
}.prototype, {
  sayHello: function() {
    console.log('Hello, I\'m ' + this.getFullName());
  },
  getFullName: function() {
    return this.firstName + ' ' + this.lastName;
  }
}).constructor;

// The way this works is that the first parameter to `$.extend` is the prototype of our constructor,
// and the second parameter is the object literal of method definitions. Because `$.extend` returns
// the target, we can't just assign the `Person2` variable to the return value of `$.extend`, but we can
// access the `constructor` of the returned prototype to set the `Person2` variable back to the constructor
// we started with.

// Example use:
var person2 = new Person2('Keegan', 'Watkins');
person2.sayHello(); // Logs "Hello, I'm Keegan Watkins"