JSON / Objects / Prototypes

all objects in JavaScript....

- are descended from Object - inherit methods and properties from Object.prototype

Arrays derive from....

Array.prototype

Functions derive from....

Function.prototype

what is JSON?

JSON is a data storage and communication format based off of JavaScript object literals - all property names are surrounded by double quotes - values are restricted to simple data: no function calls, variables, comments, or computations

what does JSON stand for?

JavaScript Object Notation

how do you retrieve an object's original prototype?

Object.getPrototypeOf(obj)

what is the default value of a constructor's prototype?

a plain, empty object that derives from Object.prototype

how do you remove a property?

delete obj.prop

using this creates a property name and value for....

every new object instantiated with the constructor - each object has its own copy - this properties are considered "own" properties (they havent been inherited

what does stringify(value) do?

returns a JSON string representation of the value passed in

what does parse(text) do?

returns an object created from the supplied JSON text

what does hasOwnProperty method do?

returns true if property was set on actual object rather than inherited

can you assign an entire object to the prototype property? if yes how

yes function Cat(){this.cute = 'very'} function Kitten(){} Kitten.prototype = new Cat(); var k = new Kitten(); console.log(k.cute);

function invocation, this refers to ....

the global object

what does a standalone function's this refer to?

the global object

in a method invocation this refers to

the object the method was called on

if you set properties on the prototype objects....

these properties are not own properties c.hasOwnProperty(c.cute) --> false bc cute is inherited

apply, call, and bind....

this is whatever you pass in as the first argument

when a function is called as a method, as in obj.method(), what will this point to?

this will point to the object that it was called on

what are some properties that are inherited from Object.prototype?

toString hasPropertyOf

what will obj.prototype return

undefined

show how Object.create works

var cat = {cute: 'very'}; var kitten = Object.create(cat); console.log(kittens.cute) //kitten inherits cute from cat

what is a constructor?

a function with the new keyword in front of it - make the first letter of a constructor uppercase - this helps distinguish between regular functions and constructors

a prototype is ....

another object that is used as a fallback source of properties

the constructor's this object is...

bound to a fresh, empty object

how else can you create an object with a particular prototype?

constructors

what does Object.create do?

creates a new object with the specified prototype object and properties

how can you add properties to an object even after its instantiated?

function Cat(){}; var c = new Cat(); Cat.prototype.cute = 'very'; console.log(c.cute)

how do you add a new property and value pair to an object?

obj.newProp = newVal obj[newProp] = newVal

how can you get/retrieve a value that's associated with a property name from an object?

obj.propName obj[propName]

what are three ways to create objects?

object literals Object.create constructors

all constructors have a property named....

prototype

in addition to their set of properties, almost all objects also have a ....

prototype

the search for a property goes on up the chain of prototypes until....

- the property is found - an object with a null prototype is reached/the last object in the chain Object.prototype

function Werewolf(mood){ this.mood = mood; } what can you think this constructor is doing when invoked with new?

function Werewolf(mood){ //this = {} this.mood = mood; //return this; }

what is Object.prototype's prototype?

null

what is the prototype of an object created with an object literal? Object.getPrototypeOf({})

Object.prototype

what is the top level prototype?

Object.prototype

what is Array.prototype's prototype?

Object.prototype - its at the top of the prototype chain - its the last object checked for properties

when an object gets a request for a property it does not have....

its prototype will be searched for the property, then the prototype's property, and so on

what are methods?

methods are functions within the context of an object