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A Healthy Comparison between SwiftUI and Storyboard

StoryboardStoryboard is a part of an interface builder which has been the most common way to create UI for iOS applications after its initial release with iOS 5. Any new iOS project has a Main. storyboard file by default.“The Interface Builder editor within Xcode makes it simple to design a full user interface without writing any code. Simply drag and drop windows, buttons, text fields, and other objects onto the design canvas to create a functioning user interface.” - Apple documentation about interface builders.A Storyboard in Xcode is a file that contains an empty canvas type screen. On it, we can drag and drop all types of objects available in the object library of Xcode. We can create almost everything from controllers to text fields to images to table views to buttons, all this without writing even a single line of code. You can add controller screens like a table view controller, navigation controller, etc. through drag and dropping from the object library. You can add segues and move through different screens. Even the smallest components like labels, images, text fields can be dragged and dropped from the object library.Advantages of Storyboard:It is easy to learn for even a beginner.With Storyboard, you can create a prototype of an app barely in an hour or two, which makes it easy to visualize the app without writing hundreds and thousands of lines of code.The storyboard object library has a vast collection of objects.It also has a large community support network.Drawbacks of Storyboard:Source control is difficult, since the storyboard code is in an XML type format it is very difficult to resolve merge conflicts as you cannot completely understand the code.While creating the application UI you have to keep in mind the Autolayout issues that they should work with all the supporting device sizes, you need to separately check on all devices using the preview option or running the app on each device.As the number of screens keeps increasing the management of storyboards can become very chaotic and as it forms a complex web-like structure.Swift UISwift UI was released with the release of iOS 13.“SwiftUI helps you build great-looking apps across all Apple platforms with the power of Swift — and as little code as possible. With SwiftUI, you can bring even better experiences to all users, on any Apple device, using just one set of tools and APIs.”-Apple documentation about swift UI.Swift UI is basically a toolkit released by apple to create UI’s in a declarative way.AdvantagesA single code can be used for all apple platforms like macOS, watchOS, iOS, etc.It offers an automatic live preview option which is like a hot reload that shows the changes made in the code immediately on view.There are no Autolayout issues as in the storyboard.It offers both drag and drops through the object library as well as writing code in the file facility.The code is simple and clean.Swift UI view elements can be easily reused, by creating smaller module files.It gives way to reactive programming by providing bindable objects.You can also mix UIKit and SwiftUI by using UIHostingController.DisadvantagesIt supports only iOS 13+ and Xcode 11+, so you cannot build lower version apps using this.It is still very new, there are not as many component options in the swift UI as in the storyboard object library. So you have to create custom views to fulfill requirements, eg: The search bar.It could be difficult for someone to switch from storyboard to swift UI as it is difficult to visualize the view hierarchy in the form of code.There is no direct way of migrating from storyboard to swift UI. This compels a developer to continue the use of the storyboard for existing apps and in lower versions.Since it is very new so there is less community support which is not the case for Storyboard.After looking at the pros and cons of both Storyboard and SwiftUI, building an app UI using storyboard is comparatively easier for a beginner, and has been for a very long time. But there are some flaws with it and those flaws have been taken care of in Swift UI.Swift UI also has its own set of flaws, but it can be seen that those flaws can be overlooked in terms of the advantages that it gives. Swift UI has a lot of potential for the future. You can also take a look at this Single view iOS application using swift UI if you want a taste of a SwiftUI application: iOS application using SwiftUI GitHub link.

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Basics of Reactive Programming In Swift (RxSwift)

Reactive programming basically means relying on entities emitting elements, subscribing to its changes and reacting to those changes. So, reactive programming saves you from having to re-check states and manually putting conditions in your code. It remarkably reduces the code lines and makes the code cleaner and easier to manage. Most importantly, it manages asynchronous code execution in a very elegant manner owing to its observable-subscriber method.This article will give you a quick skim of elements of Reactive programming in just 4 min reading time. These are some basic terminologies that are used while writing code using the Reactive Programming paradigm.Observable: it is an entity that can be of any data type and emits elements to its subscribers on happening of every different type of event. Example: it emits error on an error event, emits the received value on an onNext event, etc.Observer: This subscribes to observables and listens for changes in them and takes the programmed action on any change.Dispose Bag: A dispose bag holds disposables in it. So basically, it is used for garbage management in the files. When we create subscriptions, we keep adding them to a global dispose bag in a file. So whenever that particular files’ memory is deallocated the subscriptions are properly disposed off from the dispose bag, so this ensures there are no memory leaks in the project.Subjects: Subjects acts dual way, both as an observable as well as an observer. There are four types of subjects :Publish Subject: it starts empty and only emits new elements to its subscribers. On completion, it still emits completion to its new subscribers.Behavior Subject: Starts with an initial value and replays it or the latest element to new subscribers.Replay Subject: Initialized with buffer size and will maintain a buffer of elements up to that size and replay it to new subscribers.Async Subject: Emits only the last next event in the sequence, and only when the subject receives a completed event.5. Relays: These wrap their respective subjects, but only accept and relay the next events. You cannot add a completed or error event onto relays at all, so they’re great for non-terminating sequences. There are two types of relays: PublishRelay and BehaviorRelay.6. Operators: there are different types of operators such as filtering operators, transforming operators, time-based operators which can be chained on observables using the dot operator so that the input from the observable can be modified as per requirement.Filtering operators: these operators let you filter out the results received from the data source. There are different type of filtering you can do on data using different operators, for example, .elementAt(index): it gives the element at a particular index, .skip(n): it skips n elements emitted by data source etc.Transforming operators: these operators let you transform data received from the data source into a different type. Some examples of this are .toArray(): this operator is used to transform the received elements into an array, .map(): allows you to enter a data type and change it to another data type.Combining operators: these operators let you combine results from observables. Example: .concat(): it is a static function that combines two observable sequences, .zip: it is used to couple two operations/requests and aggregate a result once both are done.Time-based operators: these operators are used to do operations like buffering and replaying data. Example: replay(): This operator creates a new sequence which records the last ’n’ emitted by the source observable, interval(schedulers: ): it produces an infinite observable sequence of Int values (effectively a counter) sent at the selected interval on the specified scheduler.7. Schedulers: A scheduler is a context on which a process takes place. So schedulers here are used to shift subscription contexts. There are different types of schedulers like MainScheduler, Concurrent Schedulers etc. To Switch Schedulers, we use these two operators:subscribeOn(): we can switch threads by using this operator.observeOn(): this operator changes the scheduler where the observation happens.That’s all about the basics of Reactive Programming and a sneak peek into Rxswift.I hope it was helpful enough to give you a kick start on reactive programming and rxswift!Please share your valuable feedback in the comments section and also give the article a Clap if it’s worth it!

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Best Practices to Navigate Existing Project Work

Whether you need to develop a new feature, fix a bug, refactor the existing code or you just got on board of a project that is already running, as developers we have all had an existing project work at some time or are required to do so every now and then.Now you may have been able to deliver the project without any roadblocks, in which case you can use this post as best practices to follow for future projects. But most of the time developers face various challenges as they fail to ask relevant questions and clarify before starting work. Lack of thorough understanding of the project and its requirements often leads to assumptions making it difficult to approach the work systematically.To avoid such roadblocks and ensure desired results you should be aware of the approach to work on an existing project and the initial steps you need to follow before you start coding.Here’s a list of best practices that might help you initiating work on an existing project effectively.Get the right accessOne of the common problems is access permission issues that can delay deliverables. Before you begin work on a project ensure that you have the right developer-level access. And also have contact details of the relevant person in your team at hand in case you run into any access issues. Once you get your username and password do a test run to reconfirm whether you have the right access required for the job.Understand the projectIt is crucial to have a thorough understanding of the project before you start working on it. Some of the key questions listed below can help you gather right and enough information that can help you understand the project better. These questions include:Why is the project running?What problem is it solving?How is it solving the problem?Who are the end-users of your project?How frequently is a feature delivered in your project?What SDLC process is followed?Besides, clarify the requirements and do not hesitate to ask questions to your team members and clients. In addition, follow these basic yet critical steps to get a complete visibility into the project:Make sure you have access to proper documentation such as:README file, Data Flow Diagrams, Architectural Diagrams etc.Code review checklist, Non-Functional Requirements checklist, and Definition-of-Done checklist.Ways of working, dos and don’tsSecurity policies documentKnow about the version control that is used in your project (like GIT, TFS).Go through the project structure, identify the tech stack, the frameworks and the 3rd party libraries and packages used.Understand why certain libraries are being used.Be aware of the builds and deployment process, whether manual or automated.Understand the complete structure and flow of control in your project. You can refer to the documentation and make your own flowcharts, if necessary. Get them reviewed by your team members to reconfirm your understanding of the project.Request knowledge transfer sessions and invest in code time if you are starting something that is new for you but not for your team members.Set up the development environmentEvery project will have some external dependencies due to which it becomes a challenge to set up the project in dev-environment, in order to run and test locally.It is easier to solve this problem if you have a dockerized project (read more on docker here), as used in this project, so that you can run and test the project locally.Another way to solve this problem is to do a dev-environment setup manually. You can find the steps for doing the same in the README.md file, but that might not be enough.Sometimes after setting up the dev-environment, your project may not function in an expected way, and may end up throwing errors. In that case, trace the error, look up online or discuss with the team. When you find the solution, log it in a shared sheet so that others can benefit from it.These are some of the best practices I have listed on the basis of my experiences and challenges that I faced while working on existing projects.If you too have come across an issue which you think might later become a roadblock, feel free to share with the team along with the resolutions or alternatives.

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Scala XML Data Processing: Efficient Spark Pipelines

As data scientists and machine learning engineers, we don’t always appreciate that most of the data we get are usually in CSV or at times in JSON file format. In reality, this is great, as we need to deal with large volumes of data and any format that makes it easy to read and understand data should be highly appreciated. And people who work with CSV know how great this is as a data format. In this blog we will be focusing on Scala XML data processingHaving said that, it might not always be the case. If you are a Scala developer (a JVM language), you are likely to work in a Java environment. And since XML has been the preferred format for data interchange, you are most likely to receive data in an XML format. Which means, you will need to parse the data from XML files and build data pipelines out of it.XML, which stands for Extensible Markup Language, was thought of as a way in which both computers and humans should be able to understand the text. Of course, the designers got their inspiration from the hugely successful HTML. You might argue that no one actually reads HTML and we only see the final output thrown by the browsers. Well, may be, it was assumed that XML would be read only by developers and hence it should work. But then we moved to Service Oriented Architecture (SOA) where XML has become the standard data-format for communication between services. In this post we will see how we can parse XML in spark-Scala.<?xml version="1.0"?><!DOCTYPE PARTS SYSTEM "parts.dtd"><?xml-stylesheet type="text/css" href="xmlpartsstyle.css"?><PARTS> <TITLE>Computer Parts</TITLE> <PART> <ITEM>Motherboard</ITEM> <MANUFACTURER>ASUS</MANUFACTURER> <MODEL>P3B-F</MODEL> <COST> 123.00</COST> </PART> <PART> <ITEM>Video Card</ITEM> <MANUFACTURER>ATI</MANUFACTURER> <MODEL>All-in-Wonder Pro</MODEL> <COST> 160.00</COST> </PART> <PART> <ITEM>Sound Card</ITEM> <MANUFACTURER>Creative Labs</MANUFACTURER> <MODEL>Sound Blaster Live</MODEL> <COST> 80.00</COST> </PART> <PART> <ITEMᡋ inch Monitor</ITEM> <MANUFACTURER>LG Electronics</MANUFACTURER> <MODEL> 995E</MODEL> <COST> 290.00</COST> </PART></PARTS>Table 1 A simple XML file (1)Interestingly it’s quite easy to parse and create XML pipelines in Scala. To load an XML file, you will need to pass the filename to the loadFile utility from XML. Please note that parsing the whole file requires a lot of processing power and therefore, chances are that you may run into ‘OutOfMemoryError’ as shown in table 2.scala> import scala.xml.XMLimport scala.xml.XMLscala> val xml = XML.loadFile("data/Posts.xml")java.lang.OutOfMemoryError: Java heap space at java.util.Arrays.copyOf(Arrays.java:3332)...scala.runtime.ScalaRunTime$.replStringOf(ScalaRunTime.scala:345) at .$print$lzycompute(<console>:10) at .$print(<console>:6) at $print(<console>) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)Table 2 Scala code first runIn case that happens, you will need to boost the memory for the spark driver. I am allocating a random high number here (as shown in table 3).spark-shell --driver-memory 6GTable 3 Increased driver memoryNow I can parse the XML with ease (refer to table 4).scala> import scala.xml.XMLimport scala.xml.XMLscala> val xml = XML.loadFile("data/Posts.xml")xml: scala.xml.Elem =<posts> <row FavoriteCount="1" CommentCount="1" AnswerCount="1" Tags="&lt;job-search&gt;&lt;visa&gt;&lt;japan&gt;" Title="What kind of Visa is required to work in Academia in Japan?" LastActivityDate="2013-10-30T09:14:11.633" LastEditDate="2013-10-30T09:14:11.633" LastEditorUserId="2700" OwnerUserId="5" Body="&lt;p&gt;As from title. What kind of visa class do I have to apply for, in order to work as an academic in Japan ? &lt;/p&gt;" ViewCount="415" Score="16" CreationDate="2012-02-14T20:23:40.127" AcceptedAnswerId="180" PostTypeId="1" Id="1"/> <row ClosedDate="2015-03-29T20:06:49.947" CommentCount="2" AnswerCount="2" Tags="&lt;phd&gt;&lt;job-search&gt;&lt;online-resource&gt;&lt;chemistry&gt;" Title="As a computational chemist, which online resources are avail...Table 4 Read XMLI have not talked about the file data that I am using till now. The xml dataset is a stackoverflow dataset downloaded from archive.org. It contains data in this format.<?xml version="1.0" encoding="utf-8"?><posts> <row Id="1" PostTypeId="1" AcceptedAnswerId="180" CreationDate="2012-02-14T20:23:40.127" Score="16" ViewCount="415" Body="&lt;p&gt;As from title. What kind of visa class do I have to apply for, in order to work as an academic in Japan ? &lt;/p&gt;&#xA;" OwnerUserId="5" LastEditorUserId="2700" LastEditDate="2013-10-30T09:14:11.633" LastActivityDate="2013-10-30T09:14:11.633" Title="What kind of Visa is required to work in Academia in Japan?" Tags="&lt;job-search&gt;&lt;visa&gt;&lt;japan&gt;" AnswerCount="1" CommentCount="1" FavoriteCount="1" /> <row Id="2" PostTypeId="1" AcceptedAnswerId="246" CreationDate="2012-02-14T20:26:22.683" Score="11" ViewCount="725" Body="&lt;p&gt;Which online resources are available for job search at the Ph.D. level in the computational chemistry field?&lt;/p&gt;&#xA;" OwnerUserId="5" LastEditorUserId="15723" LastEditDate="2014-09-18T13:02:01.180" LastActivityDate="2014-09-18T13:02:01.180" Title="As a computational chemist, which online resources are available for Ph.D. level jobs?" Tags="&lt;phd&gt;&lt;job-search&gt;&lt;online-resource&gt;&lt;chemistry&gt;" AnswerCount="2" CommentCount="2" ClosedDate="2015-03-29T20:06:49.947" />Table 5 Our target datasetEach record is allocated a row tag, that combines multiple attributes. We can now parse these individual tags and get the value of the attributes. To parse the records, you will need to search an XML tree for the required data, using XPath expressions. The way it works is that you need to pass \ and \\ methods for the equivalent XPath / and // expressions.For example, you can get the ‘row’ tags and then on each record get the ‘body’ attribute. This gives us a sequence of scala.Option.scala> val texts = (xml \ "row").map{_.attribute("Body")}texts: scala.collection.immutable.Seq[Option[Seq[scala.xml.Node]]] =List(Some(&lt;p&gt;As from title. What kind of visa class do I have to apply for, in order to work as an academic in Japan ? &lt;/p&gt;), Some(&lt;p&gt;Which online resources are available for job search at the Ph.D. level in the computational chemistry field?&lt;/p&gt;), Some(&lt;p&gt;As from title. Not all journals provide the impact factor on their homepage. For those who don't where can I find their impact factor ?&lt;/p&gt;), Some(&lt;p&gt;I have seen many engineering departments want professional engineer registration. Why do they care? &lt;/p&gt;), Some(&lt;p&gt;What is the h-index, and how does it work ?&lt;/p&gt;), Some(&lt;p&gt;If your institution has a subscription to Journal Citation Reports (JCR), you...Table 6 Getting the appropriate textNow that you have an iterator you can run complex transformations on top of it.Below (in table 7) we are converting texts to string, trimming them for extra whitespace, then filtering out the text with some string, and converting them to lowercase.scala> val lower_texts = texts map {_.toString} map { _.trim } filter { _.length != 0 } map { _.toLowerCase }lower_texts: scala.collection.immutable.Seq[String] =List(some(&lt;p&gt;as from title. what kind of visa class do i have to apply for, in order to work as an academic in japan ? &lt;/p&gt;), some(&lt;p&gt;which online resources are available for job search at the ph.d. level in the computational chemistry field?&lt;/p&gt;), some(&lt;p&gt;as from title. not all journals provide the impact factor on their homepage. for those who don't where can i find their impact factor ?&lt;/p&gt;), some(&lt;p&gt;i have seen many engineering departments want professional engineer registration. why do they care? &lt;/p&gt;), some(&lt;p&gt;what is the h-index, and how does it work ?&lt;/p&gt;), some(&lt;p&gt;if your institution has a subscription to journal citation reports (jcr), you can check it t...Table 7 Spark transformationScala offers a convenient and easy way for basic XML processing. This post is aimed at helping beginners use XML and Scala with ease. If you found this useful, do leave a comment, we would love to hear from you and share the post with your friends and colleagues.

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Managing C# Dependencies: A Dive into Dependency Injection

Introduction:Have you ever struggled to manage C# dependencies in your projects? As your codebase grows, manually handling multiple dependencies can become daunting. Thankfully, there’s a solution that can streamline your code and improve its maintainability: dependency injection (DI). In this blog post, we’ll have a conversation where we explore a real-life scenario, discuss the challenges faced, and see how implementing dependency injection can provide an optimal solution.User: Hi there! I’ve heard much about dependency injection in C# lately, but I’m not sure how to implement it. Can you give me a beginner-friendly overview?C#: Absolutely! Dependency injection is a design pattern that helps manage the dependencies between components in your code. It allows you to write more modular and flexible code by reducing direct dependencies and promoting loose coupling.User: That sounds interesting! How can I start implementing dependency injection in my C# projects?C#: To implement dependency injection in C#, you can use a DI container or a DI framework. One popular choice is Microsoft.Extensions.DependencyInjection framework. It provides a lightweight and easy-to-use DI container. Let’s walk through an example to illustrate how it works.User: Great! I’m excited to see an example. Please show me how to use it.C#: Sure! First, you’ll need to install Microsoft.Extensions.DependencyInjection NuGet package. Once that’s done, you can create an instance of the ServiceCollection class, the DI container provided by the framework. Here’s a simple example:using Microsoft.Extensions.DependencyInjection;using System;// Define a class with a dependencypublic class Logger{ private readonly ILoggingService _loggingService; public Logger(ILoggingService loggingService) { _loggingService = loggingService; } public void Log(string message) { _loggingService.LogMessage(message); }}// Define an interface for the dependencypublic interface ILoggingService{ void LogMessage(string message);}// Implement the dependencypublic class ConsoleLogger : ILoggingService{ public void LogMessage(string message) { Console.WriteLine($"Logging message: {message}"); }}public class Program{ public static void Main() { // Configure the DI container var serviceProvider = new ServiceCollection() .AddTransient<ILoggingService, ConsoleLogger>() .BuildServiceProvider(); // Resolve the dependency var logger = serviceProvider.GetService<Logger>(); // Use the dependency logger.Log("Hello, world!"); }}In this example, we have a class called Logger that depends on an interface ILoggingService. The dependency is injected into Logger its constructor. By registering the dependency AddTransient in the DI container, we ensure that a new dependency instance is created each time it's requested.User: Ah, I see! So the DI container creates instances and injects them into the needed classes?C#: Exactly! The DI container manages the creation and injection of dependencies for you. It resolves the dependencies based on their registered types and provides them with the required classes.User: That’s convenient! Are there different ways to register dependencies in the DI container?C#: Absolutely! The ServiceCollection class provides various extension methods to register dependencies with other lifetimes. The most common ones are:AddTransient: A new dependency instance is created each time it’s requested.AddScoped: A new example of the dependency is created once per scope (e.g., per web request or logical operation).In conclusion, implementing dependency injection in our C# projects can greatly simplify managing dependencies and improve code maintainability. While Microsoft.Extensions.Dependency injection is a popular choice; we also have alternatives like Autofac, Ninject, Unity, and Simple Injector. Evaluate the features and characteristics of each framework to determine the best fit for your project. Happy coding!

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Agile Methodology Unveiled

Agile Methodology, to me, seems like a distant cousin of division of labor!Wait, before you call it a technical term!The word agile has been so much in use in the technology industry that now when we think of if it, the term seems connotative of the domain. Even, the dictionary meaning has one general definition and one specific to software development.When diving into the origin of this word or methodology, you will find that it was not connected even remotely to the technological sphere. Time and again the innovative minds of people came up with methods which gave us a glimpse of this method. Be it the formation of Shewhart Cycle (Plan-do-Check-Act) or the implementation of this in the post WWII Japan by W. Edwards Deming.However, the concept took some time to take concrete shape. It was February 2001, when 17 exponents believing in various methodologies from the world of software development decided to bring in a methodology which all agreed on. Thus, in the meeting held at Snowbird, Utah, the term ‘agile’ was adopted for this methodology and the Agile Manifesto came into existence, and so did the core value:Individuals and interactions over processes and toolsWorking software over comprehensive documentationCustomer collaboration over contract negotiationResponding to change over following a planAs we can gauge, the first half of each value gains more importance over the second half, though both are considered in the development cycle.With the changing times, it was becoming difficult to carry on the waterfall and other traditional methodologies in product development. Agile came as an answer to these difficulties and has since then proved to be efficient.This iterative process allows us to make changes as and when needed rather than wait for the entire product to be developed before we get to know about any glitches.Remember the comparison between agile and division of labor?This is where scrum comes into picture. Out of the many agile practices like XP (eXtreme Programming), DSDM (Dynamic systems development method) and FDD (Feature-Driven Development), Scrum is the most popular one.All the requirements/features of a product are termed as user stories each and these stories sum up to a product backlog. This is further divided into the release backlog which is again divided into sprints (typically a sprint extends upto two weeks or more depending on the release cycles). At the end of a sprint, it is necessary to have a ship ready product and if there is any delay, it calls for change in plan or retrospection.This brings in the concept of a burndown chart. Through this chart we get to get a clear view of the progress of the project, especially the work which is undone. This chart also helps to estimate the sprint time as well as the time when the product will be ready for release.But, how do we keep a track of all these?The Scrum (stand-up) meetings… rings a bell?Yes, these meetings are integral to a sprint planning and every day all the members of the team meet for 15 minutes to discuss the progress of the project. These meetings are mostly about three questions:(1) What they have worked on since last scrum meeting(2) What they are planning to work on in that day &(3) If there are any problems they are facingTherefore, you now know the importance of these meetings.This was a glimpse into the world of agile. We will soon be back with other aspects of it.This then, be as agile as possible. Remember! It’s not a technical term and can be applied to any sphere of life.

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Scope Chain Performance Optimization Tips

Browsers have evolved a lot in the past few years and many of the below discussed points may or may not be valid for modern browsers.However, I am just catching up with few points regarding scope chain and performance that may (or may not in modern browsers) affect the performance of web apps.Lets start with an example:While testScopeChain function is invoked, execution context sets up a stack. The local variables will be accessed first. If a variable is not found, interpreter will go deeper in the stack and keep looking till it finds the object (it is somewhat related to prototypal inheritance).function testScopeChain() {var location = document.location.href;var protocol = document.location.protocol;return (‘Location is: ‘ + location + ‘ & Protocol is: ‘ + protocol);}In the above code snippet, document is a global object. So the interpreter will look for the object in the first row of the stack first and won’t find it. It will have to traverse further to look for the object in the next row of execution stack (global object). This further traversing will take longer and may cause performance issues.The code may be refactored as:function testScopeChain() {var doc = document;var location = doc.location.href;var protocol = doc.location.protocol;return (‘Location is: ‘ + location + ‘ & Protocol is: ‘ + protocol);}Once we have a local copy of document in doc, it can be accessed locally (in the first row of the stack).Coming to closures, an extra row is added to the execution context stack.function outerScope() {var outerScopeVal = ‘Outer Scope’;function innerScope() {var innerScopeVal = ‘Inner Scope’;console.log(outerScopeVal);console.log(innerScopeVal);}innerScope();}outerScope();In the above code snippet, innerScopeVal can be accessed locally (in the first row of the execution context stack). But when it comes to the outer scope, outerScopeVal can be accessed from the next row which again may take some time.Issue with ‘with’ and ‘catch’ statements: They will add a row to the execution stack. Essentially this row will be the first one. So even local variables will be placed in the second row.Recommendations:1> Use local variables as much as possible.2> Avoid with and catch statements3> Minimize use of closures4> Always use var to prevent accidental declaration of global variable

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Elm Programming Overview

Elm programming language falls under the functional programming paradigm. It may be considered as an alternative to good old javascript for frontend web development.Salient Features:Statically typedImmutable dataNo runtime exceptionsThe Elm architectureInteroperability with JavascriptAll the elm code is compiled to Javascript. elm-html creates DOM nodes at runtime as required.Installation Set up://Install elm globally:sudo npm install -g elm//Set up package.json:elm package install//Install a specific package:elm package install package_name//Start server:elm reactorUsing elm-reactor (or elm-make without any options) generates a skeleton consisting of HTML and CSS, with a script tag containing the Elm code compiled to javascript. The Elm compiler provides two ways to compile the code:elm make Main.elm — output index.html — outputs to index.html, and contains HTML skeleton and the compiled elm code.elm make Main.elm — output elm.js — outputs to elm.js and only contains the compiled elm code.Note: Tabs are not allowed in elm.//Hello World Program:— Syntax for comments in elmmodule Main exposing (..)— Package is imported from elm-package.jsonimport Html— Html.text converts the string “Hello World” to html formatmain =Html.text “Hello World”Refresh the browser. The Hello World should reflect now

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Mastering Jasmine, a JavaScript Unit Testing Basics

“More than the act of testing, the act of designing tests is one of the best bug preventers known. The thinking that must be done to create a useful test can discover and eliminate bugs before they are coded — indeed, test-design thinking can discover and eliminate bugs at every stage in the creation of software, from conception to specification, to design, coding and the rest.” — Boris BeizerUnit Testing lets a developer validate a unit (class, function) of software. A developer may unknowingly make a change to an existing unit which could make the software go awry. Unit testing prevents such accidental cases. As soon as the developer writes some awry code for a unit, the test runner will let the person know which test case has failed.Coming to Javascript, various testing frameworks are available. Few popular ones are:MochaChaiJasmineIn the rest of the article, I would focus on few basics of the Jasmine framework.“Jasmine is a behavior-driven development framework for testing JavaScript code. It does not depend on any other JavaScript frameworks. It does not require a DOM (Document Object Model). And it has a clean, obvious syntax so that you can easily write tests.” -Jasmine Official DocumentationGetting started with Jasmine is fairly easy with below mentioned instructions:Installation:npm install –save-dev jasmineInitialise Project:jasmine initSeed Project with Examples:jasmine examplesRun Test Suite:jasmineA sample test case from the official doc looks like:describe(“A suite is just a function”, function() {var a;it(“and so is a spec”, function() {a = true;expect(a).toBe(true);});});I would dig more into this sample code.The test case typically comprises of:SuiteSpecMatcherCustom MatcherbeforeEachafterEachSuite:A test suite is a collection of test cases. The test suite does have a name (mentioned in the quotes). Below provided snippet is a typical jasmine test suite with 0 test cases.describe(“This is a jasmine test suite”, function() {});Spec:A test spec is a test specification for a unit. In jasmine, a spec starts with the keyword ‘it’ and has a spec message. Below provided snippet is a typical jasmine test spec not doing anything.it(“This is a jasmine test spec”, function() {});Matcher:Matcher is a check that lets you evaluate the output of a unit against a test result. Below provided snippet is a typical jasmine matcher.expect(func()).toBe(0);Let’s say, there is a function named func and it always returns a value 0. This function is a unit. If something goes awry with this function, the matcher will fail and hence, the unit test for the unit will fail.Custom Matchers, beforeEach, afterEach:Jasmine provides a number of inbuilt matchers. However, we can write our own custom matchers.beforeEach lets a developer define something before a spec is executed.An example would be to define a custom matcher in beforeEach and use the custom matcher in the spec. Below is a sample snippet:beforeEach(function () {this.addMatchers({toBeEven: function () {return (this.actual % 2) === 0;}});});it(‘should be even’, function () {expect(isEvenNumber()).toBeEven();});afterEach lets a developer define something after a spec is executed.How do I run tests:Jasmine provides a spec runner where you may run your tests. Another option would be to use a test runner like karma.As terminal is always fancier, a headless browser (like PhantomJS) should be preferred over Chrome.

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