What are the two categories of properties in JavaScript?

3 property descriptors 

              a property descriptor encodes the tributes of a propery as an object.each of the properties of that object corresponds to an attribute.

example read only property

whose value is 123:

{

value:123,

writable:false,

enumerable:true,

configurable:false

}

3.1 functions that use property descriptor

                                               Object.defineproperty(obj,propName,propDesc)

create or changes a property on object whose name is propname and whose attributes are specified via propdesc.

var obj=object.defineprop

value:123,

enumerable:true

//writable and configu

});