var dog=new Object()
dog.age=5
dog.hasOwnProperty("age") //returns true
dog.hasOwnProperty("favoritefood") //returns false, property doesn't exist
dog.hasOwnProperty("toString") //returns false, as toString property is inherited

Example 1:

var fruits=["apple", "grapes"]
Array.prototype.isPrototypeOf(fruits) //returns true, "fruits" in an array
Function.prototype.isPrototypeOf(fruits.slice) //returns true, fruits.slice() is a function

Example 2:

function Car(){
//Car class here
}

function Toyota(){
//Toyota object here
}

Toyota.prototype=new Car() //inherit from Car class
var Prius=new Toyota //instance of Toyota object
Car.prototype.isPrototypeOf(Prius) //returns true, Prius is an instance of Toyota which inherits from Class Car

var mycar=new Object()
mycar.size="mid"

mycar.propertyIsEnumerable("size") //returns true for local user defined property
mycar.propertyIsEnumerable("toString") //returns false for prebuilt property
mycar.propertyIsEnumerable("cost") //returns false for non existent local property

A common task for programmers to do is to override this method with something more robust, especially for custom objects. the default returned value is less than descriptive of the object. For example:

function records(){
this.records=[]
for (var i=0; i<arguments.length; i++)
this.records.push(arguments[i])
}

records.prototype.toString=function(){
return "All records: "+this.records.join(" | ")
}

var myrecords=new records("George", "Edward", "Sue")
alert(myrecords.toString()) //alerts "George | Edward | Sue"