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Coding

How to get started with IndexDb, and why..

If you have never heard of IndexDb before, do not worry, you are not going to be the first. IndexDb is a low level api that provide a non relational database, directly in your browser. This browser feature can support development in writing fully featured PWA ( progressive web app), with offline support.

In today’s article, we are going to build a service that will allow us to provide offline support for our blog. The article is going to cover the following:

  • IndexDb introduction
  • Introduction to IDB – IndexDb with Promises
  • Database setup
  • CRUD methods (Create, read, update, delete)
  • Debugging

IndexDb introduction

As briefly mentioned above, IndexDb API is not widely used from many developers, but it has actually been around for quite some time.

The use of this browser feature is usually associated with development of PWA, and more precisely to provide offline support. For my personal opinion, the main features of this API are the ability to be used within the Service worker and the possibility to store BLOB – files within its store ( tables).

Support and Space limits

If you are worried about support and or the maximum size of this database, you are going to be reassured quickly.

IndexDb browser support is quite extensive, in fact it covers over 95% of the global browser usage, as shown on caniuse.com. These statistics are very reassuring, as they are as extensive as any current framework ( vue, react, angular).

IndexDb support screenshot from caniuse.com
IndexDb browser support screenshot from caniuse.com

Even if I would suggest you all to always try to keep its usage and size to a minimum, the API comes with a considerable space quota. The avaialble amount of space that can be used by the IndexDb ( and other low level api), is browser dependent. These amounts has changed quite a few times in the last few years, but the table below, shows the current quota ( as of november 2019), gathered from the official google developer site.

table showing the store amount for indexDb in current browser. Crhome < 6%, Firefox < 10%, Safari < 50mb, ie10 < 250mb
Available space for Indexdb in modern browser from developer.google.com

Non relational database

If you have just used relational database, such as Sql or MySql, then the use of this feature, may take some time to being fully understood.

The main different is the “loose” definition of tables column and type, but a full article explaining the differences and its usage can be found on pluralsight.

Basic features

In this section we are going to introduce some of the vocabulary that will be used later in the course of this article.

Store

If you have ever worked with any sort of database, you have surely heard of Tables. When using IndexDb this are called Stores.

versions

Due to the great flexibility provided by non relational database ( ability to save different data structure ), it is vital to use its versioning feature.

Async

This is not actually a feature and/or a feature name. But just a warning to remind you that ALL features offered by IndexDb are asyncronous, and currently natively set using callbacks and events (we are going to use a library to help us with this).

Index

This low level API has the ability to create indexes within their stores. If you have never heard of indexes, in simple words, they allow you to “quickly” find entries within your store.

Introduction to IDB

IndexDb is a fantastic feature, and I really suggest you all to get your hand upon it and start using it. Unfortunately, it has a very big disadvantage, it is event driven, and it does not fit current development methodology (promises and async/await).

To help us in that, we are going to use a simple library called idb (
https://github.com/jakearchibald/idb ). There are many library out there that provide greater support, but I am faithful that the actual API is going to develop overtime, and starting to use a “fully featured framework”, may not be necessary in the near future.

This library can either be installed by NPM

npm install idb
import { openDB, deleteDB, wrap, unwrap } from 'idb';

async function doDatabaseStuff() {
  const db = await openDB(…);
}

or use it directly from unpkg

<script type="module">
  import { openDB, deleteDB, wrap, unwrap } from 'https://unpkg.com/idb?module';

  async function doDatabaseStuff() {
    const db = await openDB(…);
  }
</script>

Database Setup

It is now time to start and code our application. We are going to build a simple service that can be used to store and fetch out posts ( and as mentioned above), be used to provide content for our site in case of offline usage.

In our first step, we are going to create a database. With IndexDb we can create as many database as we want ( in fact, you may already have a few created by packages and libraries).

To create a database we need to use the openDB method. This method is going to try and open the DB, and in the case in which the database or its current version is currently available, it will “create an instance of it”.

async function _init(DB_NAME, VERSION_NUMBER) {
  _db = await openDB(DB_NAME, VERSION_NUMBER, {
    updated(){ //callback used to define the new database instance }
  });
}

_init("Blog", 1)

The above code would work as intended, as indexDB does not you to set up individual tables and column as other conventional databases.

But there may be time, when you may need to define more control to the store (table) of your database.

As I previously mentioned, the upgrade callback is the method called to support us in creating and or upgrading existing database.

For example, with the following snippets, we are going to create a couple of store (blogs, authors), and set an auto increment column called ID.

upgrade(db) {
  const storeName = ["blogs", "authors"];      
  tableNames.map(storeName =>{  
    if (!db.objectStoreNames.contains(storeName)) {
      db.createObjectStore(storeName, { keyPath: "id", autoIncrement:true });
    }
  });
}

Due to the nature of a JSON based database, this is all that is needed, and we do not need to go in details for each of the columns. The above code would be enough to run CRUD operations on the store created.

CRUD operations

It is not time to fill our database with data, and luckily this is quite simple with IDB. We are going to complete the following actions:

  • Create
  • GetAll
  • GetOne
  • Delete
  • Count

Create

In our first action, we are going to insert some data into our database. To achieve such an action, we are going to use the PUT method.

const entry = {
  "title": "my blog title",
  "content": "# my content markdown"
}

_db.put("blog", data);

GetAll and GetOne

Now that our table is starting to be filled with data, it is time to have a way to “retrieve” the data. To fetch the full content of a table, we can use the GetAll method, otherwise we would be able to retrieve a specific entry with the use of the Get method and an unique ID, and we have previously specify as the ID column with the use of the keypath method during our store creation.

IndexDB action are asynchronous, and for this reason, we are going to use the async / await methodology to wait for the promise issued by our wrapper IDB.

//get all entry
const blogs = await _db.getAll("blogs");

get a specific entry
const blog = await _db.get("blogs", 1)

Delete

There would be time when we need to remove some of the entry within our database.

Luckily, this is going to be as easy as create it. The use of the Delete method, with a specific ID would be sufficient to achieve our needs:

//delete a specific entry
_db.delete("blogs", 1);

Count

IndexDb provides us with some out of the box functionality such as the count method. This is going to return the number of entry within a specific store.

const storeEntryCount = await _db.count("blogs");

Debugging

Debugging, for me, is one of the most important feature of any new technologies I ever try out.

I am personally the kind of developer, that need to make “mistakes” to fully learn, but I also need a way to “see” this mistakes to fully learn from them.

As it turned out, IndexDb is extremely simple to debug, as you will surely already have the debugging tools needed to improve your skills: Google Chrome.

By being a developer, I assume that you are already familiar with the Chrome debugger.

Chrome debugger – Application tab – indexDb

IndexDb feature can be found within the Application tab of the debugging tool. If you have ever worked with “Local Storage” and/or “Session storage”, then introducing yourself to indexDb is going to be extremely simple.

Chrome provides us with everything we need to really make the most of this Database, with the simple UI that only google can provide.

Conclusion

IndexDb is a very powerful resource, but it lacks the resources necessary for every developer to start and use it.

If you are willing to have a little struggle with not enough resources, but are eager to get ahead on the “offline support” development, than I really hope that this blog post will provide you with enough information to get you started.

If you have any question about this article, and/or about the technology above mentioned, please do not hesitate to get in touch.

Video: 5 minutes of Dev – Flexbox Layout

The following is the first of a series of videos, designed to support developers of all levels with short recording that affects different topics.


In this video we are going to define a simple flexbox layout. Due to time constraint, this video do not go in many details, but provide enough information for developers to become aware of technologies and tools that can be used during their day to day.

If you would like to support me in defining the topics for the next videos, please do not hesitate to contact me through the website or in Twitter, and I will be more than delighted to help you, if I am able too.

How to fix git error “fatal: bad object HEAD”

During development, I stumbled upon an error in GIT that prevented me to complete any operation that required to contact remote origin (Fetch, push, etc..)

No matter which branch I was on, I would always received the following error when trying any of the above operations:

fatal: bad object HEAD

The repository in question was quite big ( over 4gb) and I wanted to find a solution that did not require me to pull a full copy of the repository down again.

The problem

The source of the issue, is a corrupted file within the GIT folder. There is no special reason for this to happen ( or at least I could not find any reasonable explanation for it), but it is not extremely common.

The code

I am going to share the solution that I have used in my specific case. It solved the issue in just a few seconds.

The following code, need to be run from the location of the affected repository.

cp .git/config .git/config.backup
git remote remove origin
mv .git/config.backup .git/config
git fetch

The explanation

The code above is self explanatory, but for the curious I will explain below line by line.

cp .git/config .git/config.backup

This line uses the command utility for copying files (read more). It is simply make a backup copy of the config file, within the .git folder

git remote remove origin

This line of code uses the remote feature of git, that has the main duty of
managing set of track repository. As explained on the official Git documentation , the remove command is used to remove all remote-tracking branches and configuration settings.

This last line of code, is the actual solution to our problem. By removing all configuration and existing files of remote branches, we remove our corrupted files.

mv .git/config.backup .git/config

We are not going to use another command utility, the one for moving files MV, as explained on the wikipedia website. The command is restoring our previously backed up config file. This step is needed to re-set all the remote branches.

git fetch

If you have ever used GIT, you will have come across the FETCH command. Running this command, will recreate all the files that we have previously removed. GIT is going to use the information within the config file, to know what branches and tags should be fetched from remote.

Conclusion

The above code helped me, and I hope it will support you in solving your issues. Please feel free to post any comment and/or suggestion to improve the above fix.

Vue Js development resource

I have been using Vue JS for the last couple of years, and I have created a set of resources that can be extremely beneficial for someone who is trying to get started or wants to have a reference to some resources throughout their development.

Disclaimer: I am not gaining any economical advantage by sharing this links and I have no affiliation with any of the following resources.

Official Vue Documentation – https://vuejs.org/v2/guide/

Vue js official documentation screenshot

The official documentation is the perfect place to reference at any point of development. It is simple to follow, kept up to date and very comprehensive. I am amazed how well it is written.

Vue Dynamic Cheatsheet https://vuejs-tips.github.io/cheatsheet/

Vue js dynamic cheatsheet scrennshot

No matter how well you know the API, a sneak peak of its extensive library it is always welcome. This simple page, have dynamic links to the official documentation mentioned above, making it a must have for any vue developer

News VueJs podcast – https://news.vuejs.org/

Image result for vue podcast

A weekly podcast created to provide Vue developers with the latest news and tutorials to stay up-to-date with their technology. Very useful to know in advance what is coming in future releases.

Vue Cheat sheet – https://www.vuemastery.com/vue-cheat-sheet/

A free cheat sheet that include all the essential vue syntax provided by the creator of Vue Mastery. This is perfect for people that like to have a visual reference to the Vue api

NativeScript – https://www.nativescript.org/vue

nativeScript, homepage screenshot

An open source framework to build truly native mobile apps. It is great to get started with their online playground and fantastic to use, as it enables you to use your Vue skills to make native app.

Codesandbox – https://codesandbox.io

codesandbox homepage screenshot

A powerful online code editor for Vue. It is packed with everything you need to get started and more. It is constantly updated with new feature, and it the one stop for any new project ideas that you may have.

Storybook https://storybook.js.org/

Storybook is a development environment for UI components. It is packed with fantastic free add-ons ( accessibility, responsiveness, dynamic variables). And it is a great resource for any mid/large Vue project. (support other framework).

Vue Devtools ( Chrome /  Firefox) – https://github.com/vuejs/vue-devtools

Chrome and Firefox DevTools extension for debugging Vue.js applications. A must have for all Vue developers. It support new Vue developer to get started by analysing the components and their state, and it is useful for experience developer to check performance, events triggering and so much more.

Vue mastery –https://www.vuemastery.com/

vue mastery banner

Vue mastery is the one stop for any training resources. They are the biggest supporters of Vue Js ( they donate part of the revenue) and often offer good deals.

Vue interview question – https://www.toptal.com/vue-js/interview-questions

A very useful blogpost provided by the toptal, that provide insight on the ‘must know’ interview question for a vue js vacancy.

Conclusion

I really hope the resources above will turn to be useful, and please do not hesitate to comment and send me a message if you think that I have missed anything that should be added.

How to debug Jasmine-es6 in visual studio code

This article is going to show the configuration required to debug Jasmine-ES6 in Visual studio code.
Jasmine-ES6 is a Helpers and overrides that augment Jasmine for use in an ES6+ environment. It is great when you have a project that you do not want to transpile using babel. And it turned out to be one of the NPM package that was used in one of the latest project in which I was involved.
Due to the nature of the plugin, it is not possible to Debug Jasmine-es6 directly in the browser, but it is possible by using the debug feature provided by Visual Studio Code. The settings that are going to be provided below, will actually work to emulate any NPM command that you are currently using.

Create a debug configuration file in Visual Studio Code.

Visual studio code enables use ( sometimes with the use of extension) to debug almost any coding language (js, c#, php,ect..).

To access the Debug page we need to click the “bug” icon on the left hand menu.

Now that we have accessed the debugging page, we are able to add our configuration. To do so, click on the dropdown next to the Green arrow, like shown in the image below.

Visual Studio Code (VSC) will provide you a list of “predefined” debugging configuration that will support you in completing the setup. In our case we are going to use the “launch program” option.
visual studio code available configuration
Our configuration file will look something like this:
Visual studio Code basic debug file
 
  1. {
  2. "version": "0.2.0",
  3. "configurations": [
  4. {
  5. "type": "node",
  6. "request": "launch",
  7. "name": "Launch Program",
  8. "program": "${workspaceRoot}/app.js"
  9. }
  10. ]
  11. }
The configuration can have multiple entry that can be accessed by the dropdown previously used.

Setting the config

The config requires two main information. The first is the Program that we would like to run, this can actually be changed with whatever program you are currently running from the command line. When writing a command you will probably just use the name of the package ( depending how it is installed ), for example “Jasmine init”.

Node will automatically know that you are looking in reality for a package within the node_modules folder called Jasmine. Unfortunately our Debug configuration file is not that clever and will require you to specify the complete path.
You can use ${workspaceFolder} to select the workspace root, and then form the rest of the path required to reach the entry js file of your package. In the case of Jasmine-es6 the path will look something like:
jasmine-es6 path
 
  1. "${workspaceRoot}/node_modules/jasmine-es6/bin/jasmine.js"
Running the above is the equivalent of running the command Jasmine-es6 in the command line. This will work, but in our case we want to be more specific and actually just run a specific spec file.
In a command line scenario I would run the following line:
Jasmine command line
 
jasmine-es6 "/tests/Tests1spec.js"
To add parameter in our configuration we need to use the specify the args array:
Args array
 
  1. "args": [
  2. "${workspaceFolder}\\tests\\Tests1spec.js"
  3. ]
If you use backslash instead than forward slash, you will have to escape them ( as shown above)

Conclusion

The above post is aimed at supporting you and hopefully save you some time. The debugging feature of Visual Studio Code are quite extensive ( I debugger PHP in the past and it worked perfectly).  Not that everything is set up, you can start debugging by clicking the green arrow in the debug page, or just by pressing F5 from your keyboard (make sure to add breakpoint where you would like the add to break).

There may be better method to debug, and most people would have webpack setup to support them in the traspilation and test run, but I wanted to go against current and try something different.

As always I am happy to receive any comment that can support the future readers.

I complete the post wit the complete file below:

Node Program debug in Visual Studio Code
 
  1. {
  2. // Use IntelliSense to learn about possible Node.js debug attributes.
  3. // Hover to view descriptions of existing attributes.
  4. // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
  5. "version": "0.2.0",
  6. "configurations": [
  7. {
  8. "type": "node",
  9. "request": "launch",
  10. "name": "Launch Program",
  11. "program": "${workspaceRoot}/node_modules/Jasmine-es6/bin/jasmine.js",
  12. "args": [
  13. "${workspaceRoot}/tests/Test1spec.js"
  14. }
  15. ]
  16. }

 

"