Prototypes

var Person = function(name) {
  this.name = name;
}

Person.prototype.greet = function(){
  console.log("Hi, " + this.name);
}

var Developer = function(name, skills) {
  Person.apply(this.arguments);
  this.skills = skills || [];
}

Developer.prototype = Object.create(Person.prototype);
Developer.prototype.constructor = Developer;

var dev = new Developer("Jhon", ["js", "php"]);