Javascript Inheritance:

The Journey to Class

(simple)

- Min @ongmin

Inheritance: Classical

- Instances inherit from a blueprint (the class).

 

- Create sub-class relationships.

Inheritance: Prototypal

- Instances inherit from other instances. 

 

- Objects Linking to Other Objects (OLOO)

Here's the fun part (Proto)

Almost everything in JavaScript is an object.. 

Objects contain named properties

obj.propName || obj['propName']

Each object has an internal property called prototype, which links to another object.

The prototype object has a prototype object of its own, and so on – aka the prototype chain.

Visually, a Prototype Chain looks like this...

It doesn't go on forever... 

If you follow an object’s prototype chain, you will eventually reach the core Object prototype whose prototype is null. This signals the end of the chain.

Inheritance: Classical

- Instances inherit from a blueprint (the class).

 

- Create sub-class relationships.

Inheritance: Prototypical

- Instances inherit from other instances. 

 

- Objects Linking to Other Objects (OLOO)

JavaScript does not have classes, but we can program as though it does. 

Hello ES6 classes!

Diagram

- OLOO

- Constructor form

Prototypal inheritance (previous)

Here:
-Relationships and delegation are identical.

-The memory usage is identical.

-The ability to create many "kids" is identical.

OLOO relies on Object.create() to create a new object which is [[prototype]]-linked to another object. 

Le After: ES2015 Classes

ES2015: 

Syntactical sugar over the Objects and prototypes that we're used to working with.

Clean way to create objects and deal with inheritance.

Le Before: Constructor

Le After: ES2015 Classes

Sources

http://wildlyinaccurate.com/understanding-javascript-inheritance-and-the-prototype-chain/

https://medium.com/javascript-scene/the-two-pillars-of-javascript-ee6f3281e7f3

http://www.crockford.com/javascript/inheritance.html

http://www.udemy.com

http://stackoverflow.com/questions/29788181/kyle-simpsons-oloo-pattern-vs-prototype-design-pattern

Diagram

Classical Inheritance

Swiss Inheritance

Parasitic Inheritance

Class Augmentation

Object Augmentation. 

Other things..

For my own further readings

Javascript Inheritance: The Journey to Class

By Min Ong

Javascript Inheritance: The Journey to Class

5 minutes lightning talk given at Talk.JS on 15th Dec 2015. Just a short overview of how we got to 'Classes' in ES2015, when really JS doesn't have traditional Class Inheritance.

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