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Introduction to JS

• https://jsbin.com
  • Run HTMS, CSS, JS online

What is JavaScript?

• JavaScript is a dynamic, weakly typed programming language which is compiled at runtime.
• It can be executed as part of a webpage in a browser or directly on any machine (“host environment”).
• JavaScript was created to make webpages more dynamic (e.g. change content on a page directly from inside the browser).

Cookies

• Cookies are small strings(max size 4KB) of data that are stored directly in the browser.
• They are a part of the HTTP protocol, defined by the RFC 6265 specification
• Sent to server on ecah request
• Cookies are usually set by a web-server using the response Set-Cookie HTTP-header.
• One cookie must not exceed 4KB, 20+ cookies per site(depends on the browser)

Javascript learning path

1. How The Web Works

• Type the URL and press Enter
• The URL gets resolved
• A Request is sent to the server of the website
• The response of the server is parsed
• The page is rendered and displayed

Method Resolution order

• MRO defines the order in which the base classes are searched when executing a method.
• First, the method or attribute is searched within a class and then it follows the order we specified while inheriting

Property Decorators

@property is a built-in decorator in python language which is used to make functions like getters, setters, deleter in a class behave as class properties.

Make a method behaves as attribute/variable

Magic Methods

Magic Methods are also known as Dunder methods, Special methods

Python dunder methods are the special predefined methods having two prefixes and two suffix underscores in the method name. Here, the word dunder means double under (underscore).

These special dunder methods are used in case of operator overloading (they provide extended meaning beyond the predefined meaning to an operator).

5. Inheritance

It is a mechanism that allows you to create a hierarchy of classes that share a set of properties and methods by deriving a class from another class. Inheritance is the capability of one class to derive or inherit the properties from another class.

• It specifies that the child object acquires all the properties and behaviors of the parent object.
• It provides re-usability of the code.

4.1 Encapsulation in Python

• Access modifier are useful to attain encapsulation
• It is archived by access modifiers public, private, protected

Python does not have strong distinctions between private and public variables like Java does.

There is no private-ness in python, as one of Python principles says –> We're all adults

# They just follow convention
Single underscore `_`
    --> its suppose to be protected
Double underscore `__`
    --> Do not use this field directly

# It is called Name Mangling

3. Methods in python

• Function
  • Function is block of code that is also called by its name(independent)
  • Function does not deal with Class and its instance concept.
• Methods
  • Method is called by its name, but it is associated to an object (dependent)

The following are various types of allowed methods:

1. Instance Methods - - self
2. Class Methods - - cls
3. Static Methods

Type Checking/Annotations in Python

• Type Annotations are a new feature added in PEP 484 that allow for adding type hints to variables.
• They are used to inform someone reading the code what the type of a variable should be.
• This brings a sense of statically typed control to the dynamically typed Python
• Usage

  • Annotate Argument
  • Annotate Return type
  • Annotate Variable