Prototypal Inheritance & OOP

5. The 2 Pillars Closures and Prototypal Inheritance/16 - 25.md

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+## Prototypal Inheritance
+
+Inheritance is an object getting access to the properties and methods of another object through the prototypal chain.
+
+in JavaScript, we do not have classical inheritance, though the `class` keyword. it called *syntactic sugar*.
+
+`isPrototypeOf`. `hasOwnProperty`.
+
+##### 'object'.\_\_proto\_\_ === 'Constructor'.prototype
+
+```javascript
+var arr = []
+
+// prototypal chain
+arr.__proto__ === Array.prototype
+Array.prototype.__proto__ === Object.prototype
+Object.prototype.__proto__ === null
+
+// Array Constructor and Object Constructor are also objects (functions). 
+// they inherit from base Function. but as constructors, the `prototype` property matters.
+// Only function has `prototype` property. that's why function could be Constructor.
+Array.__proto__ === Function.prototype
+Object.__proto__ === Function.prototype
+```
+
+[JavaScript Object Hierarchy](http://www.mollypages.org/tutorials/js.mp)
+
+[The JavaScript Object Paradigm and Prototypes Explained Simply](https://levelup.gitconnected.com/the-javascript-object-paradigm-and-prototypes-explained-simply-e9cb9eaa49aa)

6. Object Oriented Programming/1 - 18.md

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+# Programming Paradigm
+- clear and understandable
+- easy to extend
+- easy to maintain
+- memory efficient
+- dry
+
+enable us to make complex code more organized.
+
+Scheme(function) + Java(object) ==> JavaScript
+
+## Object-Oriented Programming
+Bringing together the data and its behavior in a single location. modeling real world objects and relationships.
+
+1. copy and paste obj code --> 2. function factory --> 3. OOP
+
+#### `Object.create()`
+
+#### Constructor Function
+`new` keyword
+
+#### Prototypal-Based Programming & Class-Based Programming(syntactic sugar)
+prototype. `class` keyword.
+
+##### `public` & `private(`#`)` - in staging(2019-07-28)
+
+##### review `this` keyword:
+- `new` binding
+- implicit binding. inside obj.
+- explicit binding. `bind`. `call`. `apply`
+- arrow function. lexical binding.
+
+### Inheritance
+`extend` keyword. 
+
+```javascript
+class B extends A {}
+
+B.prototype.__proto__ === A.prototype
+
+A.prototype.isPrototypeOf(B.prototype)
+```
+
+### Four Pillars of OOP:
+- Encapsulation.
+wrap things are related.
+
+- Abstraction.
+hiding the complexity and creating simple interface.
+
+- Inheritance.
+avoid repetitive code, memory effeciency.
+
+- Polymorphism. the ability in programming to present the same programming interface for differing underlying forms.