JS: Property Descriptor

What is Property Descriptor

Property Descriptor is the syntax for specifying Property Attributes . It has the form:

{ value: value, writable: boolean, enumerable: boolean, configurable: boolean }

Property Descriptor for Getter Property

{ get: function, enumerable: boolean, configurable: boolean }

〔see Getter Setter Properties〕

Property Descriptor for Setter Property

{ set: function, enumerable: boolean, configurable: boolean }

Get Property Descriptor

Property Descriptor is used by several JavaScript functions to create/set properties together with attributes.

• JS: Object.getOwnPropertyDescriptor
• JS: Object.getOwnPropertyDescriptors
• JS: Reflect.getOwnPropertyDescriptor

Set Property Descriptor

• JS: Object.create
• JS: Object.defineProperty
• JS: Object.defineProperties

Default Values of Property Descriptor

value

undefined

configurable

false

enumerable

false

writable

false

set

undefined

get

undefined

// check default values of property attributes

const xx = Object.create( Object.prototype, { "p":{value:1} } );
const desc = Object.getOwnPropertyDescriptor(xx, "p");

const defaultX = new Map(
[ ["value", 1],
["writable", false],
["enumerable", false],
["configurable", false] ]);

console.log(
 Object.entries ( desc ) . every (([k,v]) => (v === defaultX.get(k)))
);
// true