This is a simple cheat sheet about JavaScript objects. It is just my collection of notes I have been collecting on using and working with JS objects.

// literal notation object
var james = {
  job: "programmer",
  married: false,
  speak: function( feeling ) {
    console.log("Hello, I am feeling " + feeling);
};

// property detection in objects with hasOwnProperty
if ( james.hasOwnProperty("job") ) {
  console.log(james.job);
}
else {
  james.job = "Student";
  console.log(james.job);
} 


// constructor notation logic
function Person(first, last, job, married) {
  this.firstname = first; 
  this.lastname = last; 
  var age = 0; // age is private
  this.job = job;
  this.married = married;

  this.speak = function() {
    console.log("Hello");
  };

  // this public method return the age
  this.getAge = function(){
    return age;
  };

  // this is a private function
  var toggleMarried(){
    this.married = ! this.married;
  };
}

// create a "gabby" object using the Person constructor
var gabby = new Person("student", true);


// inheritance with prototype
// chain of inheritance and going up the chain to find properties

function Animal(name, numLegs) {
  this.name = name;
  this.numLegs = numLegs;
  this.isAlive = true;
}
function Penguin(name) {
  this.name = name;
  this.numLegs = 2;
}
function Emperor(name) {
  this.name = name;
  this.saying = "Waddle waddle";
}

// set up the prototype chain
Penguin.prototype = new Animal();
Emperor.prototype = new Penguin();

var myEmperor = new Emperor("Jules");

console.log( myEmperor.saying ); // should print "Waddle waddle"
console.log( myEmperor.numLegs ); // should print 2
console.log( myEmperor.isAlive ); // should print true


//Creating objects, properties and functions
var students = ["Joseph", "Susan", "William", "Elizabeth"]

var scores = [ [80, 70, 70, 100],
               [85, 80, 90, 90],
               [75, 70, 80, 75],
               [100, 90, 95, 85] ]

var average = function( array ) {
  var total = 0;
  for (var i = 0; i < array.length; i++){
    total += array[i];
  }
  return total / array.length;
};               

// create a gradebook object
var gradebook = {};

// create a property for each of the students and give each corresponding scores
for ( var i = 0; i < students.length; i++ ){
  gradebook[students[i]] = {};
  gradebook[students[i]].testScores = scores[i];
}

// add a function to add a score to a student
gradebook.addScore = function(student, score){
    this[student].testScores.push(score);
};

// add a function to get a student's average score
gradebook.getAverage = function( student ){
  return average(this[student].testScores);
};