node.js

Write Clean Javascript Code

A awesome resouce on writing clean javascript code
https://github.com/ryanmcdermott/clean-code-javascript

based on Robert C. Martin's book
Clean Code: A Handbook of Agile Software Craftsmanship

"The only valid measurement of code quality is WTFs/minute"

Variables

  • Use meaningful and pronounceable variable names
  • Use the same vocabulary for the same type of variable
  • Use searchable names
  • Use explanatory variables
  • Avoid Mental Mapping
  • Don't add unneeded context
  • Use default arguments instead of short circuiting or conditionals

Functions

  • Function arguments (2 or fewer ideally)
  • Functions should do one thing
  • Function names should say what they do
  • Functions should only be one level of abstraction
  • Remove duplicate code
  • Set default objects with Object.assign
  • Don't use flags as function parameters
  • Avoid Side Effects
  • Don't write to global functions
  • Favor functional programming over imperative programming
  • Encapsulate conditionals
  • Avoid negative conditionals
  • Avoid conditionals
  • Avoid type-checking
  • Don't over-optimize
  • Remove dead code

Objects and Data Structures

  • Use getters and setters
  • Make objects have private members

Classes

  • Prefer ES2015/ES6 classes over ES5 plain functions
  • Use method chaining
  • Prefer composition over inheritance

SOLID

  • Single Responsibility Principle (SRP)
  • Open/Closed Principle (OCP)
  • Liskov Substitution Principle (LSP)
  • Interface Segregation Principle (ISP)
  • Dependency Inversion Principle (DIP)

Testing

  • Single concept per test

Concurrency

  • Use Promises, not callbacks
  • Async/Await are even cleaner than Promises

Error Handling

  • Don't ignore caught errors
  • Don't ignore rejected promises

Formatting

  • Use consistent capitalization
  • Function callers and callees should be close

Comments

  • Only comment things that have business logic complexity.
  • Don't leave commented out code in your codebase
  • Don't have journal comments
  • Avoid positional markers

Microservices, APIs, SOA

I found a great article on "Microservices, SOA, and APIs: Friends or enemies?"
check it out.. really easy to understand the differences

https://developer.ibm.com/tutorials/1601_clark-trs/

A little bit about Microservices:

It's often said.. complex code is spaghetti code (with meatballs = OOP), well structured layered code is lasagne code.. and microservices ravioli code.

  • Complex Spaghetti Code
  • Well Layerd Code
  • Ravioli Code ( Microservices )

On bigger applications.. a well thought out monolithic modular app might not be enough or at least not performant enough.

Big companies like Netflix talk about it.
https://www.nginx.com/blog/microservices-at-netflix-architectural-best-practices/

The millions of users require:

  • fast startup times,
  • easy and reactive ui,
  • working movies (main functionality),
  • no downtimes and
  • always new features/updates.

The solution to this of course is a microservice application

Thoughts before creating microservice instead of monolithic applications:

  • Do you need to scale? How much concurrent users do you have?
  • Does your application or several parts really need to have a high-availability?
  • Do you develop in separate teams or is everyone on one team?

Benefits

  • Scalability:
  • Microservices can be monitored really well, giving you metrics to find services with high hardware requirements or faulting services
  • run multiple instances for particular services, making reaction times really fast by also giving you a high availability (in case they crash)
  • You can run/scale on multiple Servers / PaaS Instances (Pivotal, AWS, ...) with different spec requirements depending on what your microservices needs
  • Improved Isolation:
  • every Microservice should be one logical part and thus can be updated or refactored or exchanged separate without affecting the others
  • By doing only one particular job (bounded context).. your microservices become easier to read, test and optimize
  • You can use multiple programming languages in one project. eg. node.js, ruby, c#, python, c, R.. in the end you talk via API
  • Background Services:
  • You can run background jobs, which wait for events to start working. they can do things without your interaction.

Disadvantages

  • Distributed System Complexity (Logging, Monitoring, Network, Msg Queues, Multiple Instances, )
  • with more Services, more parts can fail
  • Architecture causes network-load and can be slowed down by network-latency
  • May have double code for same helper functionalities

Programming Services it is highly recommended to apply the principles of

12 Factor Apps

https://12factor.net/

  • Code is Version controlled with many deploys [Codebase]
  • Dependencies are declared and isolated in a manifest [Dependencies]
  • Configurations are stored in ENVironment variables, not config files [Config]
  • Service are attached Resources, which can be consumed over Network (local or 3rd Party) and can be detached at will [Backing Service]
  • Build and Run stages are seperated. Providing a faster, tested and better Release Management. [Build, release, run]
  • Services are Stateless. They share nothing. They only use persistent data from backing stores. Thus they can easily be scaled. [Process]
  • To fit the concurrency needs, services are exported via Port Binding. [Concurrency]
  • Processes should be designed to be disposable without hassle [Disposable]
  • You should have a similar Developement and Production environment, designed for continuous integration. [Dev/Prod parity]
  • Logs should be treated as Event Streams. The App should never be concerned of storing logs. [Logs]
  • Management Tasks running as Processes: no local terminal, no direct db access. [Admin processes]

React.js Tutorials

Right now I'm absorbing React.js tutorials/best practice for a new project I'm about to do. I'm going to write here soon about it.

Here are some great React Tutorials I found:

The videos is really good to follow and its practical.
They are usually between 5-15 min

In general I can recommend every YouTube tutorial by

The Net Ninja

Here are more of those

Clap