prototypesPractice.js

// 1. Write a function that returns the object on a given object's prototype chain where a property is defined. 
// See the example code below:


// function getDefiningObject(object, propKey) {
//   // check to see if object has property
//   // - if yes, return object
//   // - if no, get prototype of the object
//   //  - repeat check
//   do {
//     if (object.hasOwnProperty(propKey)) {
//       return object;
//     } else 
//     object = Object.getPrototypeOf(object);
//     console.log(object);
//   } while(object !== null)
//   return null;

// }

// let foo = {
//   a: 1,
//   b: 2,
// };

// let bar = Object.create(foo);
// let baz = Object.create(bar);
// let qux = Object.create(baz);

// bar.c = 3;

// console.log(getDefiningObject(qux, 'c') === bar);     // => true
// console.log(getDefiningObject(qux, 'e'));             // => null

// 2. Write a function to provide a shallow copy of an object. 
// The object that you copy should share the same prototype chain as the original object, 
// and it should have the same own properties that return the same values or objects when accessed. 
// Use the code below to verify your implementation:

// function shallowCopy(object) {
//   let result = Object.create(Object.getPrototypeOf(object));
//   let prop;

//   for (prop in object) {
//     if (Object.prototype.hasOwnProperty.call(object, prop)) {
//       result[prop] = object[prop];
//     }
//   }
//   return result;
// }

// let foo = {
//   a: 1,
//   b: 2,
// };

// let bar = Object.create(foo);
// bar.c = 3;
// bar.say = function() {
//   console.log('c is ' + this.c);
// };

// let baz = shallowCopy(bar);
// console.log(baz.a);       // => 1
// baz.say();                // => c is 3
// console.log(baz.hasOwnProperty('a'));  // false
// console.log(baz.hasOwnProperty('b'));  // false

// 3. Write a function that extends an object (destination object) with contents from multiple objects (source objects).

function extend(destination, ...extensions) {
  extensions.forEach(extension => {
    let properties = (Object.getOwnPropertyNames(extension));
    properties.forEach(prop => destination[prop] = extension[prop]);
  });
  console.log(destination);
  return destination;
}

let foo = {
  a: 0,
  b: {
    x: 1,
    y: 2,
  },
};

let joe = {
  name: 'Joe'
};

let funcs = {
  sayHello() {
    console.log('Hello, ' + this.name);
  },

  sayGoodBye() {
    console.log('Goodbye, ' + this.name);
  },
};

let object = extend({}, foo, joe, funcs);

console.log(object.b.x);          // => 1
object.sayHello();                // => Hello, Joe