Object constructor & methods

This only provides a summary. See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object for detailed usage.

"Reflex" global object methods are more preferred to use instead of the Object methods described here.

As a constructor

'Object' can be used as constructor (new Object()) but has no advantage over using object literal.

Property Descriptor

See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty

value: the value

writable: true/false

get & set: function as getter/setter, or undefined

configurable: true - type of this property descriptor may be changed and property may be deleted

enumerable: true/false, if show up during enumeration of the properties

Prototype Property

[NOTE: should not confuse 'prototype' property with prototype. 'prototype' property is just a property, named 'prototype'. Prototype is actually an internal link. Use Object.getPrototypeOf & Object.setPrototypeOf to retrieve & set. Can also obtain with __proto__ - an accessor.

Object.prototype: the prototype of all objects

Object.prototype.constructor : the function that creates an object's prototype (overridden, by object instance's prototype's constructor property, which points to the class function)

C.prototype.constructor === C // true

Object.getPrototypeOf(ci).constructor === C // true

Object manipulation methods

Object.assign(target, source1, source2...) : copy properties of enumerable own properties from source(s) to target; note: target.assign(source1, source2) does not work

Object.create( prototype) : create an object with given prototype

Object property manipulation methods

Object.defineProperty() Object.defineProperties(): defines property of object with given name and property descriptor (writable etc.)

Object.fromEntries(): reverse of Object.entries() (note: not in node 8.10...)

Object.getOwnPropertyDescriptor(object, 'propertyName'): return property descriptor

Object.getOwnPropertyDescriptors(anObject): returns an object with descriptor of all properties, e.g. returnedObj.property1.writable...

Type, Prototype, Extension...

Object.setPrototypeOf(); Object.getPrototypeOf():

Object.preventExtensions()

Object.isExtensible()

Object.freeze(); Object.isFrozen()

Object.seal(); Object.isSealed()

Seal prevents add/delete properties & configure existing properties, freeze further prevents modifying value of existing properties

Object (own enumerable string properties) property enumeration methods

Object.entries(): returns an array of [key, value] of all own enumerable string properties; usage "for (let [key, value] of Object.entries(object1)) {"

Object.keys(): return array of names of own enumerable string properties

Object.values(): an array containing values of own enumerable string properties

Object (own) properties

Object.getOwnPropertyNames(): return names of own enumerable & non-enumerable properties

Object.getOwnPropertySymbols(): return array of all symbol properties

Comparison, Conversion

Object.is() : Compare two values. Equates all NaN values