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Wednesday, 21 February

00:34

The Beginners Guide to the GreenSock Animation Platform freeCodeCamp - Medium

A primer to creating timeline based animations without knowing JavaScript

Introduction

The GreenSock Animation Platform (GSAP for short) is a powerful JavaScript library that enables front-end developers and designers to create robust timeline based animations. This allows for precise control for more involved animation sequences rather than the sometimes constraining keyframe and animation properties that CSS offers.

The best part about this library is that its lightweight and easy to use.

With GSAP, you can start creating engaging animations with little to no knowledge of JavaScript.

This guide will show how to set up and use GSAPs TweenMax feature and also dive into a bit of Club GreenSocks DrawSVG plugin. Each of the examples below has a corresponding CodePen link so you can follow along in another tab.

Getting Started

Before coding, we first need to add the GSAP library to our HTML file. To do this, you will need to grab the CDN link to the TweenMax library. You can find links to TweenMax and other GSAP CDNs here.

Note: CDN stands for Content Delivery Network. This means that instead of hosting the JavaScript files on your site, an outside source like CloudFlare can host them for you.

Once you have the CDN link, insert it in a <script> tag at the bottom of your HTML file like so:

<script src=https://cdnjs.cloudflare.com/ajax/libs/gsap/1.20.3/TweenMax.min.js"></script>

Thats all you need to get started! If youre using an online development environment like CodePen, you can install GSAP by editing the Pen Settings.

Click the gear icon next to the JS text editor and search for TweenMax to install it in CodePen

Understanding Tweens

Tweens are the basic animation functions from within GSAP. To animate any HTML object, we must call the object, define the properties that we are going to animate, the duration of the animation, the animations easing, and any other parameters like delay timing.

For example, if we were to change a red rectangles color to black while also moving it down and to the right, the Tween would look like this in JavaScript:

TweenLite.to(#rectangle, 2, {
left:100,
top: 75,
backgroundColor:"#000000",
ease: Power4.easeIn
});
This tween gives us a rectangle that moves diagonally and changes color.

Lets break this down:

Tw...

00:28

Reactive programming and Observable sequences with RxJS in Node.js freeCodeCamp - Medium

Dealing with asynchronous non-blocking processing has always been the norm in the JavaScript world, and now is becoming very popular in many other contexts. The benefits are clear: an efficient use of resources. But the benefits come at a cost: a non-trivial increase in complexity.

Over time, vendors and the open source community have tried to find ways to reduce such complexity without compromising the benefits.

Asynchronous processing started with callbacks, then came Promise and Future, async and await. Recently another kid has come to townReactiveX with its various language implementationsbringing the developers a new powerful tool, the Observable.

In this article, we want to show how Observables implemented by RxJs (the JavaScript embodiment of ReactiveX) can simplify code to be executed with Node.js, the popular server-side JavaScript non-blocking environment.

A simple use caseRead, Transform, Write, and Log

To make our reasoning concrete, lets start from a simple use case. Lets assume we need to read the files contained in Source Dir, transform their content and write the new transformed files in a Target Dir, while keeping a log of the files we have created.

ReadTransformWriteLog

Synchronous implementation

The synchronous implementation of this use case is pretty straightforward. In a sort of pseudo code representation, we could think of something like:

read the names of the files of Source Dir
for each file name
read the file
transform the content
write the new file in Target Dir
log the name of the new file
end for
console.log('I am done')

There is nothing special to comment here. We can just say that we are sure of the sequence of execution of each line and that we are sure that things will happen as described by the following flow of events. Each circle corresponds to the completion of an I/O operation.

The sequence of events in a synchronous world

What happens in an asynchronous non-blocking environment like Node.js

Node.js is an asynchronous non-blocking execution environment for JavaScript. Non-blocking means that Node.js does not wait for I/O or Network operations to complete before moving to the execution of the next line of code.

Processing one file

Reading and writing files are I/O operations where Node.js shows its non-blocking nature. If a Node.js progra...

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Tuesday, 20 February

20:55

Exploring the what and the why of Redux freeCodeCamp - Medium

What in the world is Redux and why do I need it?

I asked myself this question when I started learning how to build single page apps (SPA) to include rich interaction on my apps. SPA has the ability to re-render different parts of the UI without requiring server round-trip.

This is achieved by separating the different data, which represent the state of the application, from the presentation of these data.

The view layer renders a representation of these data to the UI. A view can be made up of different components. As an example, consider an online store with a product listing page. The page could contain components that represent the different products and their prices, a visual count of the total items in the cart, and a component to suggest similar products to the purchased items.

The model layer contains data to be rendered by the view layer. Each component in the view are independent of each other, each rendering a predictable set of UI elements for the given data, but multiple components can share the same data. When there is a change in the model, the view re-renders and updates the component affected by the model update.

The Problem

The application state can be stored in random objects in-memory. Its also possible to keep some state in the DOM.

But having the state scattered around can easily lead to unmanageable code. It gets hard to debug. If multiple views or components share similar data, its possible to have that data stored in a different memory location, and the view components will not be in sync with each other.

With a separation of views from models, data gets passed from the model to the view. If there are changes based on user interactions, this will update the model and this model update could possibly trigger an update to another model and also update another view component which can also trigger an update to a model.

One of the known issues with this unpredictable flow of data was the notification bug on Facebook. When youre logged in to Facebook, you see a notification for new messages. When you read it, the notification clears. After some interactions on the site, the notification comes up again, then you check and there are no new messages and the notification clears. When you interact more with the app, the notification comes back again and this goes on in a cycle.

The Aim

It is easy to add complexity to the code if the state isnt managed properly. Therefore, it is better to have one place where the data lives, particularly when the same data has to be shown in multiple places in the view. With a haphazard flow of data, it becomes hard to reason about state changes and predict the possible outcome of a state change.

The solution: Unidirectional data flow and single source of trut...

06:04

What Music Can Teach Us About The Way We Share Code freeCodeCamp - Medium

What Music Can Teach Us About How We Share Code

Is that a Cello-playing ape?

Not that long ago, many of us were carrying a suspicious-looking suitcase in the back of our cars, or had one hidden under our beds. Some of us had Ikea-made towers with multiple storage spaces standing proud in our living rooms. In both cases, this was the result of our impressive music CD-Roms collection. Today, chances are they are nostalgically stored in our garage.

After a short reign, music CD-Roms were replaced by iTunes and YouTube, with MP3 players in between. This revolution happened mainly because of 5 major disadvantages CDs had from day one:

  1. They were cumbersome to use, carry and handle.
  2. They took too much effort to purchase/create.
  3. They were very hard to change and modify. Nobody really wanted to burn a new CD whenever a new Bieber song came out (dont judge me).
  4. They forced us to carry a bunch of songs we dont listen to and zap through them just to listen to a single song we really wanted to listen to.
  5. Who remembered which songs were on which CD? 90% of my burned CDs contained the same 10 songs anyways.

Surprisingly, this isnt all that different from the way we share code today, between projects and between people. Lets see how.

How on earth is that like sharing code?

I usually just like to listen to my light-saber swooshing back and forth

Modularity has always been the holy grail of software development, and the key to better reusability, maintainability and testability.

Every day, more of the applications we build are designed with greater modularity through smaller components of code. Reusable functionalities, UI and Web components (such as React, Vue and Angular), Node.js modules, GraphQL APIs and even serverless functions are our building blocks.

Now lets be honestwho knows exactly which reusable components were written in their codebase, organizes them, and shares them between their projects at scale? I know I didnt. Then, I started asking myself why not.

Let me show you. Here is a React movie application hosted on GitHub. As you can see, it contains a total of 49 files and 14 directories. One of these directories is the components sub-directory. Inside that sub-directory there are 8 reusable React components (such as hero and navigation).

 src
    App.js
    App.scss
    App.test.js
    components
       hero
       hero-button
       item
       list-toggle
       logo
   ...

05:03

How I won a trip to Google by learning to code freeCodeCamp - Medium

Cant wait to visit the place :)

Setting the scene

Im a sixteen-year-old teen, and this is the story of how I went from noobie to becoming a Google Code-In (GCI) winner. Google Code-in is an international contest to introduce pre-university students (ages 1317) to open source software development.

There are cool prizes as you advance through the competition: digital certificates, t-shirts, hoodies, and finally the Grand Prize Trip to Google HQ. This years edition had over 3500 students from 78 countries who completed 16468 tasks.

No story is complete without a flashback. Bear with me, as I bring you back in time. The good parts of the story grow more meaningful when you understand whats going on backstage :)

Spoiler: The lessons learned were more valuable than the actual prize. So stick around until the end.

$journey[0] = Day 0 Zero D;

486 days ago (16 months but fancier)

I was in 10th grade back then. I didnt know how to program. All I knew about the subject from school was that HTML was a programming language. Pseudo-code? Nah, never heard of it. Python was the name of a reptile back then. Now I know its actually a beast.

One fateful day though, everything changed. While flipping through a (borrowed) textbook, I came upon a flyer. It was about the schools robotics club. Quite a shabby-looking thing, with Comic Sans splattered everywhere. The designer in me writhed in pain, but me being me, I decided to give it a shot. That moment was my launch into the wonderful world of programming.

The first thing we learnt was visual programming with Scratch. We used it to tinker with robotics kits like Hummingbird and Finch. As someone with no prior knowledge of code, I found Scratch convenient. The fact that we used it for practical purposes concretized my opinion.

Through Scratch, we made our monstrous creation pour a glass of water. It was one year later that Id realise that Python would have been a better start.

$journey[1] = $events["Infotech", "GCI" ];

439 days ago

December was quickly approaching. Our robotics club wanted to take part in the annual tech exhibition (...

04:50

How I built a Twitter Bot for #100DaysOfCode freeCodeCamp - Medium

A few weeks back I joined the #100DaysOfCode challenge with the aim of coding, learning and shipping more. I totally recommend you checking it out, as its an awesome community of like-minded and super friendly coders.

The community will bring you probably the most favorites, retweets and new connections youve probably ever had on Twitter. But showing your love back to your fellow coders takes away precious coding time. So I did something about it. 

I built a Bot to automatically favorite all #100DaysOfCode tweets so that I could spend more time on coding.

Building and hosting a Twitter bot.

Today Ill be showing you how to build and host a Twitter bot. Its super simple, and if you get stuck just reach out to me on TwitterI dont bite. 

Step #1: Setup a Twitter application

Create a Twitter application by following the steps below:

  • Create a new...

03:55

How writing 106 articles in a year has helped me grow as a designer freeCodeCamp - Medium

Stanley Dai

Consistency was never my strong suit. When I was younger, I remember kids my age keeping diaries or journals. My mom even got in the phase where she bought me a journal in the hope that I would write.

What was the point? I thought. Sure, it would be nice to look back to see what 9 year old me thought about life, but the main issue was that I was scared of making mistakes in my writing. I was scared that my writing would become a fabrication of events I had experienced with every fiber of my body in a moment of time.

My writing wasnt authentic. I wouldnt be able to convey my thoughts in an eloquent way. I hated the way I sounded. I never considered myself a writer so why start? These were some of the thoughts that ran in my young mind for a long time.

It wasnt until my junior year of college when I experienced an event which changed the trajectory of my growing design career: My interview experience with Microsoft.

At that time, I had developed this facade where I thought I was a great designer, and that the pace at which I was learning was totally fine. I didnt think of pushing myself to learn further, as I would probably do that once I started working. I was already in a good place in that I was getting all these interviews! That was validation enoughor so I thought.

When I found out that I got rejected from Microsoft, I was hurt. I didnt know how to handle the rejection. I had worked so hard, and I thought I did great. Anyone who has gotten rejected knows how soul-sucking and bone-crushing the feeling is.

It wasnt until this moment that I realized the way I was putting myself down was toxic, and I hated the fact I was making myself feel useless. I knew I had a lot more growing to do if I wanted to do big things and if I wanted to handle rejection in a way that encouraged action.

And action it was. I started reflecting on my experience to see where I could improve and put my feelings aside. I wanted to come to terms with rejection, but I wanted to do it in a way that would give insight to my interview experience for people interested in tech and preparing for interviews.

This is when I started writing about my Microsoft Onsite Interview Experience for the whole world to read. It was a way to reconcile the bitterness of rejection, so I could look back on my experience and improve from it moving forward.

As a result of writing about my experience, I was surprised to receive lots of encouragement and gratitude for sharing my story. I also found that when I was writing, I enjoyed the process of it all. I loved crafting a story, reflectin...

02:42

Things you need to know about working with SVG in VS Code freeCodeCamp - Medium

Check out this VS Code release highlights video from Brian Clark. Towards the end, he shows how you can now zoom in on image previews in VS Code.

https://medium.com/media/c16a0c2b19ef8f89977ee5fb74725423/href

I thought that was an interesting feature. I mean, lets face itthere are only two types of people in the world: those who like to zoom in on images and those who wont admit it. So I opened a project that I had to test it out and sure enough, it works as advertised.

My next thought was to see if it worked on SVG images. Because I like to zoom in on SVG and watch it not degrade. At this point in my life, that is an enjoyable and fulfilling activity.

It turns out that VS Code does not provide a visual preview for SVG files from within the editor. Which makes sense. SVG is markup and VS Code treats SVG files like XML, which is only text. You would need XSLT to render it into something you could view. I just triggered a bunch of you, and for that, I apologize.

Here is a great joke about XML to soothe your anxiety:

XML is like violence: If it isnt working, you arent using enough of it
- Unknown

This got me wondering, if VS Code treats SVG like XML, what extensions are available to help me work with SVG in VS Code? It turns out that there are quite a few, and some work better than others. Here are a few of my favorite extensions for working with SVG in VS Code.

SVG

The first extension is just called SVG.

Thats right. This person was first to the game and got the coveted SVG name all to themselves. Like the person who registered the Twitter name Burke. What the heck, Sam! You havent tweeted in.YOUVE NEVER TWEETED!

Sam, if youre reading thistweet at me and lets talk. Seriously. You dont even wa...

02:31

How to get started with Word2Vec and then how to make it work freeCodeCamp - Medium

The idea behind Word2Vec is pretty simple. Were making an assumption that the meaning of a word can be inferred by the company it keeps. This is analogous to the saying, show me your friends, and Ill tell who you are.

If you have two words that have very similar neighbors (meaning: the context in which its used is about the same), then these words are probably quite similar in meaning or are at least related. For example, the words shocked, appalled, and astonished are usually used in a similar context.

Using this underlying assumption, you can use Word2Vec to surface similar concepts, find unrelated concepts, compute similarity between two words, and more!

Down to business

In this tutorial, you will learn how to use the Gensim implementation of Word2Vec and actually get it to work. Ive long heard complaints about poor performance in general, but it really is a combination of two things: (1) your input data and (2) your parameter settings.

Note that the training algorithms in the Gensim package were actually ported from the original Word2Vec implementation by Google and extended with additional functionality.

Imports and logging

First, we start with our imports and get logging established:

# imports needed and logging
import gzip
import gensim
import logging
logging.basicConfig(format=%(asctime)s : %(levelname)s : %(message)s, level=logging.INFO)

Dataset

Our next task is finding a really good dataset. The secret to getting Word2Vec really working for you is to have lots and lots of text data in the relevant domain. For example, if your goal is to build a sentiment lexicon, then using a dataset from the medical domain or even Wikipedia may not be effective. So, choose your dataset wisely.

For this tutorial, I am going to use data from the OpinRank dataset from some of my Ph.D work. This dataset has full user reviews of cars and hotels. I have specifically gathered all of the hotel reviews into one big file which is about 97 MB compressed and 229 MB uncompressed. We will use the compressed file for this tutorial. Each line in this file represents a hotel review.

Now, lets take a closer look at this data below by printing the first line.

https://medium.com/media/1e75a348ddf74e7585ee71162918d79a/href

You should see the following:

b"Oct 12 2009 \tNice trendy hotel lo...

01:19

Learning the basics of Conversational UI with a UX Designer for Amazons Alexa freeCodeCamp - Medium

https://arstechnica.com/gadgets/2017/05/amazon-alexa-ads-voicelabs/

During my internship at Intuit last summer, I was part of a hackathon team that created a conversational UI experience. We interviewed a few people who had experience in this field, and I had the opportunity to interview Angela Nguyen. Angela is a UX designer at Amazon, working on the Alexa Team. You can view her work here.

What is your process for designing conversational user interfaces?

It depends on the conversation. I work mostly with shopping questions, because I am on shopping team.

My process always starts with the customer and what their needs are.

For example, if they are trying to buy paper towels, then the first thing I do is think about the AIs response. Is it going to return paper towels based on having already purchased it or the present situation? Where are they making this order, or are they able to make an order via credit card? It depends on the criteria of this person, because every person asking the same question can result in the AI answering a different way.

Every situation is different for every person.

Lets say a given person always buys paper towels, and maybe its the same towels. I like to create a tree of answers (mind mapping). It starts with that one question, depending on the circumstance of this person. This person bought this towel many times, so Alexa might respond with: Do you want to buy paper towels again? If you never bought a towel, the AI might recommend a brand.

How do you design a UI designed for voice or chatbots?

There are headless devices, voice products that dont have a face or UI. This is completely voice UX. Then there are face devices which have a screen, kind of like Siri.

When designing for products with a face, it is good to consider the question, Do you want to show the same graphics as the voice is saying? If a voice says, I have paper towels that are $10 and delivered in 2 hours, will it have the image, price, etc or just the image? It is just good to consider if a person is viewing something.

Can we simplify the graphics or voices?

A good example of this is YouTube. If you ever watch a video and you land on the page, the video starts playing, but you can still scroll down to the videos while watching the main one.

While your brain is comprehending the audio, your eyes are taking in other information. The human brain can multi-task, so when we hear audio and are given visuals, they dont have to match. You can be listening and looking at comments at the same...

Monday, 19 February

23:25

Calling All Math Teacher Bloggers and Homeschoolers: Carnival Time! Denise Gaskins' Let's Play Math

The monthly Playful Math Blog Carnival (formerly Math Teachers at Play) is almost here.

If youve written a blog post about math, wed love to have you join us!

Posts must be relevant to students or teachers of school-level mathematics (that is, anything from preschool up to first-year calculus). Old posts are welcome, as long as they havent been published in recent editions of this carnival.

Click here to submit your blog post

Dont procrastinate: The deadline for entries is this Friday, February 23. The carnival will be posted next week at Give Me a Sine blog.

Have you noticed a new math blogger on your block that youd like to introduce to the rest of us? Feel free to submit another bloggers post in addition to your own. Beginning bloggers are often shy about sharing, but like all of us, they love finding new readers.

Would You Like to Host the Carnival?

Help! I cant keep the carnival going on my own.

Hosting the blog carnival can be a lot of work, but its fun to meet new bloggers through their submissions. And theres a side-benefit: The carnival usually brings a nice little spike in traffic to your blog.

If you think youd like to join in the fun, read the instructions on our Playful Math Blog Carnival homepage. Then leave a comment or email me to let me know which month youd like to take.

Explore the Other Math Carnivals

While youre waiting for next weeks carnival, you may enjoy:


[Night At The County Fair photo (top) by Bob Jagendorf (CC BY-NC 2.0) via Flickr.]


howtosolveproblemsWant to help your kids lea...

19:40

Brighton campaign reaps rewards Council to boost youth work spending by 90K IN DEFENCE OF YOUTH WORK

 

pre-qual

Pre-Qual on the streets of Brighton a year ago

 

Almost exactly a year ago we were congratulating the Brighton Protect Youth Services campaign on its creative and successful defence of youth provision in the town. In the aftermath the Pre-Qual group in a thoughtful and challenging blog concluded:

If this campaign to protect youth services has proved one thing, it is that when you organise around a demand which is achievable, have an argument which is strong enough and you pursue that argument with enough persistence and a great enough diversity of tactics, you can achieve concrete success. These were the key elements which won the youth service campaign; saving the service was realistically achievable, the arguments were solid and we simply did not leave the council alone, pursuing every possible avenue available to us, from getting out onto the streets to legally challenging the consultation process. By following this formula we believe that we can be successful in fighting off the cuts again next year, but we...

05:39

An introduction to animated transitions with React Router freeCodeCamp - Medium

In this article well look at how to animate your route transitions with React Router by breaking down the Animated Transitions example on the React Router docs.

Ive created a video to go with this article if youd prefer that:

https://medium.com/media/932ad95922945190f2023014a23ec240/href

If youre reading this youve probably discovered that React Router doesnt come with a solution for animated transitions out of the box. That ties into React Routers philosophy. It gives you routing primitives that you can build on and trusts that you can figure out the rest.

Because every app has different needs, this approach is typically the safest. The downside of this is that itll take some extra work to get the exact functionality you want. The tool well be using alongside React Router in this article is the React Transition Group.

React Transition Group is an animation library that gives us a way to perform animations when a React component enters or leaves the DOM. When paired with React Router, this is exactly what we want.

Because theres a lot going on in this article, theres going to be some setup we need to take before we ever even start talking about animations. Feel free to skip ahead if youd like.

First, lets walk through the type of app were going to be building.

Animations aside, the goal is to make it so the user can go to /hsl/:h/:s/:l or /rgb/:r/:g/:b and see the associated HSL or RGB color for those specific values.

Example with an RGB color

Example with an HSL color

To do this, well rely heavily on React Router URL Parameters. If youre not familiar with those, I recommend reading this post before continuing.

By looking at the images above, we know were going to need a few different things before we even start looking at animated transitions:

  1. An app skeleton
  2. A navbar
  3. A...

05:38

CSS Specificity Explained By Hopelessly Shopping for New Clothes freeCodeCamp - Medium

If you have ever wandered into a department store or other clothing store, then you can understand how CSS selectors apply their styles.

If you are a beginner to CSS, you have probably seen plenty of scenarios already where CSS styling rules conflict. You think that you just added a new style to an element, but after refreshing the browser many times you realize that the style is not being applied for some reason.

Heres an example. Lets say that you have a general rule that all paragraph tags should have a line-height of 140%, like this.

p{ 
line-height:140%;
}

But, you also want to create a subtitle class that will have a line-height of 120%, which will usually apply to paragraph elements.

.subtitle{ 
line-height:120%;
}

So, which one will apply when you assign it like so?

<p class="subtitle"> This is a subtitle</p>

The answer is the subtitle class styling, but I want to find a better way to explain the rules behind this logic. You dont want to open the Inspector every time you are unsure which styling is more specific..

Heres a scenario to help: imagine you are a salesperson in a department store or other clothing store. You get paid based on how many pieces of clothing you sell over the course of the day, so you need to spend your time with the best customers if you want to make the most money.

The customers that look most likely to buy get precedence. The customers that come in with a specific idea of what they want are more likely to buy.

CSS operates in a similar way. It will give precedence to the most specific styles, which will override less-specific styles. The most common ways to add style are:

  • Element level (p tag)
  • Class level (.subtitle)
  • ID
  • In-line styling

Here is how to tell which of the selectors above are most specific. In each case, the customer is looking for a tailored suit, and you must sell as much clothing as possible.

Element SelectorsOnly Having a Vague Idea

Have you ever wandered into a department store with only a vague thought, like I need a suit for an event next week.?

From personal experience, I can tell you that this is a great way to get stuck in the store for hours, trying on random suits. Anyway, these types of customers will take the longest time to find something they like. They will need to talk to a few people and try on multiple suits. Their mental image of what they want looks like this:

Yeah, they have no idea what they want. They still need to pick a style, find thei...

05:19

Programming the genome with CRISPR freeCodeCamp - Medium

How scientists edit genomes with the help of computers

CRISPR (pronounced crisper) is part of a bacterial immune system evolved to remember and remove invading viral DNA.

Its name is short for Clustered Regularly Interspaced Short Palindromic Repeats. But despite its mouthful of an acronym and complex biological origins, its engineering application is straightforward. To get started, there is only one protein you need to understandCas9.

Cas9 searches for a specified DNA sequence and cuts it by breaking both strands of the DNA molecule. This protein is useful to researchers because they can program it to target any DNA sequence. A sgRNA (single guide RNA) molecule determines the sequence that Cas9 binds to. RNA is a biological molecule similar to DNA, that can bind to proteins and DNA.

sgRNAs are short sequences with a constant region and variable region. The constant region attaches the sgRNA to the Cas9 protein. The variable region causes Cas9 to bind to the DNA sequence that complements it (see the diagram below).

The Cas9 protein bound to the DNA when the PAM sequence is on the forward (top) strand. The bold sequence is the target sequence, the green sequence is the sgRNA, and the three blue characters are the PAM. The triangles show where Cas9 will cut the DNA.

Making sgRNA is cheap and fast. This allows researchers to quickly set up a Cas9 experiment that cuts any DNA sequence. Well, not actually any sequence. There is a small constraint: the target sequence must be flanked by the correct PAM (protospacer adjacent motif)a short sequence of DNA.

Luckily, the motif NGG occurs roughly once every 42 basepairs in the human genome. This mean that researchers can find a target site near almost every sequence of interest.

Depending on the experimental set up, these cuts in the DNA can either cause a random change or a precise change to the DNA sequence (more on this later).

Before jumping into writing this program, I recommend studying the Cas9 diagram below.

The Cas9 protein bound to a DNA sequence when the PAM sequence is on the reverse (bottom) strand.

Note that DNA and RNA have a directionality based on their chemical structure. One end of the molecule is referred to as the 5` (five-prime) end, and the...

05:02

Security Vulnerabilities Explained with Rivers and Parties freeCodeCamp - Medium

Security vulnerabilities can be boring to learn. But you still need to learn them, unless you want some hacker to delete all your production databases. To make it a bit more entertaining, I tried to explain 3 major vulnerabilities in terms of every day life. So without further delay lets begin.

Man-in-the-middle attack

When you open a website you are connecting to a server. You can imagine this connection like a river and the data (for example Tweets in Twitter) are messages in bottles that float down the river.

If Alex (the server) wants to send you a dinner invitation he has to put it in a bottle and send it down the stream. But what if John (the attacker) takes the bottle out of the river and changes the message into an insult, then puts it back in the river? You will have no way of recognizing that the message you received hadnt been sent by the Alex!

This is called a Man-in-the-middle attack.

To solve this you and Alex can decide that you will write your messages reversing the order of the characters. For example, secret message becomes egassem terces.

John doesnt know the method you used to generate the secret code, so he cant understand what the message says nor change whats written on it without you noticing.

This is what the HTTPS protocol does, just with a fancier method.

DoS and DDoS

Another way you can see a server is like your homes Inbox. You receive mail, read them and reply.

What if John starts to write you a ton of mail? You wouldnt be able to respond to Alexs dinner invitation in time, because you would be too busy replying to all the other Spam messages sent by John.

This is called a Denial-of-service attack, DoS in short.

A way to mitigate this is reading the sender on top of the mail before opening it. If its John then dont bother opening the mail. This way you dont need to reply to John and can focus on handling serious stuff, like Alexs dinner invitation.

This is IP Blacklisting in a nutshell, only with digital sender internet protocol addresses.

Unfortunately John convinced a lot of other evil people to send you Spam mails. So now you cant simply discard Johns mails, because there are lots of people writing you.

This is a Distributed Denial of Service (DDoS) and its very hard to deal with.

One way to handle this is to receive mail only from Alex. Its unfortunate that your other friends wont be able to write you, because you will discard their emails too. But desperate times call for desperate measures. But gradually, you can increase the number of legitimate people youd like to receive mail from.

This is called IP Whitelisting and can be used...

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