Flo  D'Amore

Flo D'Amore

1602578847

Types, Type Systems and TypeScript

What is it all about?

type system is a set of rules for performing various consistency and correctness checks in a program. There are various definitions and classifications for type systems. A good working definition is the following:

_In programming languages, a type system is a logical system comprising a set of rules that assigns a property called a “type” to the various constructs of a computer program, such as variables, expressions, functions or modules. — _Wikipedia

There are different categorizations of type systems including:

  • Static vs. Dynamic
  • Structural vs. Nominal
  • Strong vs. Weak (this is more contentious)

Click here for a comparison of various programming languages and their type systems

Structural vs. Nominal

In a _Nominal type system, _all types are either declared or named explicitly. This type of system is used both for determining equivalence between two items, as well as sub type relationships. The majority of statically typed languages (including Java, C, C#, and Rust) use this type of system.

The_ structural type system _is based on properties of the type and any item matching the properties can pass the equivalence test. **TypeScript **(_Go is another language) _uses a structural type system.

To better understand this, let’s define an interface to capture any I/O response and also implement a class HttpResponse for this interface.

Now a function that will take IOResponse as an argument and print the details.

Image for post

#type-systems #programming #typescript

What is GEEK

Buddha Community

Types, Type Systems and TypeScript

The Definitive Guide to TypeScript & Possibly The Best TypeScript Book

TypeScript Deep Dive

I've been looking at the issues that turn up commonly when people start using TypeScript. This is based on the lessons from Stack Overflow / DefinitelyTyped and general engagement with the TypeScript community. You can follow for updates and don't forget to ★ on GitHub 🌹

Reviews

  • Thanks for the wonderful book. Learned a lot from it. (link)
  • Its probably the Best TypeScript book out there. Good Job (link)
  • Love how precise and clear the examples and explanations are! (link)
  • For the low, low price of free, you get pages of pure awesomeness. Chock full of source code examples and clear, concise explanations, TypeScript Deep Dive will help you learn TypeScript development. (link)
  • Just a big thank you! Best TypeScript 2 detailed explanation! (link)
  • This gitbook got my project going pronto. Fluent easy read 5 stars. (link)
  • I recommend the online #typescript book by @basarat you'll love it.(link)
  • I've always found this by @basarat really helpful. (link)
  • We must highlight TypeScript Deep Dive, an open source book.(link)
  • Great online resource for learning. (link)
  • Thank you for putting this book together, and for all your hard work within the TypeScript community. (link)
  • TypeScript Deep Dive is one of the best technical texts I've read in a while. (link)
  • Thanks @basarat for the TypeScript Deep Dive Book. Help me a lot with my first TypeScript project. (link)
  • Thanks to @basarat for this great #typescript learning resource. (link)
  • Guyz excellent book on Typescript(@typescriptlang) by @basarat (link)
  • Leaning on the legendary @basarat's "TypeScript Deep Dive" book heavily at the moment (link)
  • numTimesPointedPeopleToBasaratsTypeScriptBook++; (link)
  • A book not only for typescript, a good one for deeper JavaScript knowledge as well. link
  • In my new job, we're using @typescriptlang, which I am new to. This is insanely helpful huge thanks, @basarat! link
  • Thank you for writing TypeScript Deep Dive. I have learned so much. link
  • Loving @basarat's @typescriptlang online book basarat.gitbooks.io/typescript/# loaded with great recipes! link
  • Microsoft doc is great already, but if want to "dig deeper" into TypeScript I find this book of great value link
  • Thanks, this is a great book 🤓🤓 link
  • Deep dive to typescript is awesome in so many levels. i find it very insightful. Thanks link
  • @basarat's intro to @typescriptlang is still one of the best going (if not THE best) link
  •  
  • This is sweet! So many #typescript goodies! link

Get Started

If you are here to read the book online get started.

Translations

Book is completely free so you can copy paste whatever you want without requiring permission. If you have a translation you want me to link here. Send a PR.

Other Options

You can also download one of the Epub, Mobi, or PDF formats from the actions tab by clicking on the latest build run. You will find the files in the artifacts section.

Special Thanks

All the amazing contributors 🌹

Share

Share URL: https://basarat.gitbook.io/typescript/

Author: Basarat
Source Code: https://github.com/basarat/typescript-book/ 
License: View license

#typescript #opensource 

Ruth  Nabimanya

Ruth Nabimanya

1620633584

System Databases in SQL Server

Introduction

In SSMS, we many of may noticed System Databases under the Database Folder. But how many of us knows its purpose?. In this article lets discuss about the System Databases in SQL Server.

System Database

Fig. 1 System Databases

There are five system databases, these databases are created while installing SQL Server.

  • Master
  • Model
  • MSDB
  • Tempdb
  • Resource
Master
  • This database contains all the System level Information in SQL Server. The Information in form of Meta data.
  • Because of this master database, we are able to access the SQL Server (On premise SQL Server)
Model
  • This database is used as a template for new databases.
  • Whenever a new database is created, initially a copy of model database is what created as new database.
MSDB
  • This database is where a service called SQL Server Agent stores its data.
  • SQL server Agent is in charge of automation, which includes entities such as jobs, schedules, and alerts.
TempDB
  • The Tempdb is where SQL Server stores temporary data such as work tables, sort space, row versioning information and etc.
  • User can create their own version of temporary tables and those are stored in Tempdb.
  • But this database is destroyed and recreated every time when we restart the instance of SQL Server.
Resource
  • The resource database is a hidden, read only database that holds the definitions of all system objects.
  • When we query system object in a database, they appear to reside in the sys schema of the local database, but in actually their definitions reside in the resource db.

#sql server #master system database #model system database #msdb system database #sql server system databases #ssms #system database #system databases in sql server #tempdb system database

Flo  D'Amore

Flo D'Amore

1602578847

Types, Type Systems and TypeScript

What is it all about?

type system is a set of rules for performing various consistency and correctness checks in a program. There are various definitions and classifications for type systems. A good working definition is the following:

_In programming languages, a type system is a logical system comprising a set of rules that assigns a property called a “type” to the various constructs of a computer program, such as variables, expressions, functions or modules. — _Wikipedia

There are different categorizations of type systems including:

  • Static vs. Dynamic
  • Structural vs. Nominal
  • Strong vs. Weak (this is more contentious)

Click here for a comparison of various programming languages and their type systems

Structural vs. Nominal

In a _Nominal type system, _all types are either declared or named explicitly. This type of system is used both for determining equivalence between two items, as well as sub type relationships. The majority of statically typed languages (including Java, C, C#, and Rust) use this type of system.

The_ structural type system _is based on properties of the type and any item matching the properties can pass the equivalence test. **TypeScript **(_Go is another language) _uses a structural type system.

To better understand this, let’s define an interface to capture any I/O response and also implement a class HttpResponse for this interface.

Now a function that will take IOResponse as an argument and print the details.

Image for post

#type-systems #programming #typescript

Christa  Stehr

Christa Stehr

1599315360

Nominal typing in Typescript

Nominal & structural typing

Type systems are typically categorized as either structural or nominal. Languages like Java and Scala have primarily nominal type systems, whereas a language like Typescript has a structural type system. Let’s take a brief look at both systems.

Nominal Typing

In a nominal typing system, type compatibility is checked using the name of the types. If they do not have the same name, then they are not compatible; end of story. **If **Typescript had a nominal typing system the type check for the last line would fail:

Image for post

Structural typing

Typescript uses structural typing to decide whether two types are compatible with one another or not. What do we mean by structural typing? Well, let’s consider the following code snippet:

Image for post

To determine whether the type of the constant color(RGBA) is compatible with the type of serializeColor’s parameter x(RGB) the type system must verify that each member of RGB has a corresponding compatible member in RGBA. In this case, RGB has a single member color for which RGBA has a corresponding member with the same type — [number, number, number] — and so it passes the type check. Notice how the type system ignores the additional members that exist on RGBA (alpha).

#typescript #type-safe #type-systems

Lawrence  Lesch

Lawrence Lesch

1623118800

Typescript — Supercharged Features Of A Typed-system

I have been writing Typescript a lot lately. I’m using it when I work on personal projects or when I’m working with a team. At first, I was just snowed under the fact that I would have to write so much more code and that didn’t really motivate me to pick it up. But that didn’t really stop me from not trying at all. I’ve read so many compelling blogs that proved why Typescript is a must-try and how it helps build scalable web applications, that I couldn’t help but try and get a taste for myself.

I wanted a resource that will help me get started. I went through the  React Typescript Cheatsheet which helped me learn the essence right away. I also used a course from  educative.io that helped me understand the building blocks and pieces. Once I was there I almost instantly knew that even though I was writing more code, I made my codebase very predictable and maintainable so to speak.

So here I am trying to get across the features that helped me adopt Typescript almost instantly. I’m pretty sure there are tons of benefits of a typed system, but I would just mention a few that I’m liking the most.

1. Code Navigation

We have a users.service file that imports a User class. A lot of times it might happen that you can’t quite remember or not sure what the shape of the User object might be, or a teammate of yours wanted to check out your code.

2. Code Predictability

3. Code Refactoring

4. Less-error code

5. Better IntelliSense

#typescript #type-systems #blog #development #technology