obj_augmentation.js

//Augmenting the JS objects (NOTE : in JS function are objects)

//Ugly
function makePerson(first, last) {
  return {
    first: first,
    last: last
  };
}
function personFullName(person) {
  return person.first + ' ' + person.last;
}
function personFullNameReversed(person) {
  return person.last + ', ' + person.first;
}

s = makePerson("Simon", "Willison");
console.log(personFullName(s) ); // "Simon Willison"
var tmp = personFullName(s)
console.log(tmp); // "Simon Willison"
console.log(personFullNameReversed(s) ); //"Willison, Simon"


//Bad
// Why Every time we create a person object we are creating two brand new function objects within it 
function makePerson(first, last) {
  return {
    first: first,
    last: last,
    
    fullName: function() {
      return this.first + ' ' + this.last;
    },
    
    fullNameReversed: function() {
      return this.last + ', ' + this.first;
    }
  };
}


s = makePerson("Simon", "Willison")
console.log(s.fullName() ); // "Simon Willison"
console.log(s.fullNameReversed() ); // "Willison, Simon"


//Bad1 Constructor inovocation pattern
// Why Every time we create a person object we are creating two brand new function objects within it 
function Person(first, last) {
  this.first = first;
  this.last = last;
  this.fullName = function() {
    return this.first + ' ' + this.last;
  };
  this.fullNameReversed = function() {
    return this.last + ', ' + this.first;
  };
}

var s = new Person("Simon", "Willison");


//Bad2 
//No extra function object creation
function personFullName() {
  return this.first + ' ' + this.last;
}
function personFullNameReversed() {
  return this.last + ', ' + this.first;
}

function Person(first, last) {
  this.first = first;
  this.last = last;
  this.fullName = personFullName;
  this.fullNameReversed = personFullNameReversed;
}

//Good
//Person.prototype is an object shared by all instances of Person. It forms part of a lookup chain (that has a special name, "prototype chain"): any time you attempt to access a property of Person that isn't set, JavaScript will check Person.prototype to see if that property exists there instead. As a result, anything assigned to Person.prototype becomes available to all instances of that constructor via the this object.
function Person(first, last) {
  this.first = first;
  this.last = last;
}

Person.prototype.fullName = function() {
  return this.first + ' ' + this.last;
};

Person.prototype.fullNameReversed = function() {
  return this.last + ', ' + this.first;
};



//Using string exmple
String.prototype.reversed = function() {
  var r = "";
  for (var i = this.length - 1; i >= 0; i--) {
    r += this[i];
  }
  return r;
};

var s = "Hello world!";

console.log(s.reversed())

String.method('reverse',function() {
    
  var r = "";
  for (var i = this.length - 1; i >= 0; i--) {
    r += this[i];
  }
  return r;
} );

console.log(s.reverse())