Homework #1: create instances without the `new` operator

create_instance.js

/** Write a function that will emulate the behavior of the `new` operator.  I
 * should be able to pass it a constructor function and some arguments, and get
 * back an instance of it.  Here's a test case; just fill in the
 * `createInstance` function.
 *
 * You can just run the code to see if it works; if it doesn't work, assert will
 * throw errors.
 *
 * To run it, just use `node create_instance.js`
 */

function createInstance() {
  // Fill in here...
}


// constructor function for our test case
function Person(name, age) {
  this.name = name;
  this.age = age;
}

Person.prototype.sayHi = function() {
  return 'Hi, my name is '+this.name+'.';
};


// Some assertion functions we can play with
function assert(condition, message) {
  if(!condition) {
    throw new Error(message);
  }
}

function assert_equal(obj1, obj2) {
  assert(obj1 === obj2, 'Expected '+obj1+' to equal '+obj2+'.');
}


// The actual test case:
var david = createInstance(Person, 'David', 28);

assert_equal(david.constructor, Person);
assert_equal(david.name, 'David');
assert_equal(david.age, 28);
assert_equal(david.sayHi(), 'Hi, my name is David.');
assert_equal(david.hasOwnProperty('name'), true);
assert_equal(david.hasOwnProperty('age'), true);
assert_equal(david.hasOwnProperty('sayHi'), false);