property-descriptors.js

/***************************************
Property Descriptors Methods and Usage

Object.defineProperty(obj, propName, {} )
Object.defineProperties(obj, props)
Object.getOwnPropertyNames(obj)
Object.getOwnPropertyDescriptor(obj, prop)
Object.getOwnPropertyDescriptors(obj)
Object.keys(obj) - list of enumerable properties
Object.values(obj) - list of enumerable prop values

obj.propertyIsEnumerable(prop)
obj.hasOwnProperty(prop)

Objects can be
1. Extensible - new properties added
2. Frozen - props cannot be changed in any way
3. Sealed - props can't be deleted or configured
          but are still writable

Object PROPERTIES can be 
1. Writable - change the value
2. Enumerable - seen through a for...in loop
3. Configurable - change the property descriptors

Object.isExtensible(obj)
Object.isFrozen(obj)
Object.isSealed(obj)
Object.preventExtensions(obj)
Object.freeze(obj)
Object.seal(obj)

Descriptor Groups
DATA            ACCESSOR          
value           get
writable        set
configurable    configurable
enumerable      enumerable
****************************************/
let log = console.log;
let obj = {
    name: 'Bob',
    age: 45
};
Object.defineProperty(obj, 'test', {
    value: 'Shagadelic',
    writable: true,
    configurable: true,
    enumerable: false
} );

Object.defineProperty(obj, 'frank', {
   configurable:true,
    enumerable: true,
    get: () => this.value,
    set: (_val) => {
        this.value = _val + " baby!";
    }
});



for( let prop in obj){
    log(prop);
}
log( obj, obj.test, obj.frank );
obj.frank = 'Shagadelic';
log(obj.frank);