Review of the Fundamentals of ReactJS

As I go through the motions of post graduation job searching, I wanted to go back to the basics as a way to solidify my knowledge on everything I learned in the past four months. In this series that I have titled as “Back To Basics”, I take a look at broad topics and break it down to its core. Maybe it can help another fellow programmer going through a boot camp or a refresher for anyone who needs it.

In this article, I will be going over the fundamentals of React. I will be breaking down the core concepts…


Welcome back to Confusion: Part 2. I mean Scopes & Closures: Part 2. If you missed the first part where I talked about scopes, you can find it here.

In this part, I will be going over closures! Closures can be a scary and intimidating topic. Just look blow at how MDN defines it:

A closure is the combination of a function bundled together (enclosed) with references to its surrounding state (the lexical environment).

In this article I will breakdown the concept with some examples. …


It’s been exactly 4 months since I learned JavaScript. If you asked me 4 months ago to explain scope and closures, I would run away embarrassed. It was a topic I dreaded and understood at a surface level. Even after graduating from Flatiron School’s Software Engineering program, the topic haunted me in my technical interviews. I took it for granted and did not realize how crucial and fundamental the concept was. So here I am to set the story straight and re-introduce scopes and closures.

Let's talk about Scope!

Scope simply refers to the visibility and accessibility of variables, functions, and other expressions. Anything…


In React applications, we use components to split and isolate different parts of the web user interface into individual pieces. These pieces act independently and use a render function to return React elements in JSX. These elements describe how that section should be displayed to the user.

Each component goes through three phases: mounting, updating and unmounting. You can also think of it as our natural life cycle: we are born, we grow (adolescence and adulthood), and eventually, we die. React components are created by being mounted onto the DOM, they change or grow through updates, and finally, they can…


To understand Object Oriented Programming in JavaScript, we first have to understand that JavaScript is not a class-based language. This can be a little confusing since class is a keyword used for syntax. In other languages, like ruby, we define classes that act as “blueprints” for objects. They serve as templates while objects are instances of those classes. Inheritance of attributes and methods occur through classes.

In JavaScript, however, we solely use objects for inheritance. Classes were introduced in ECMAScript 2015. It does not support class based object oriented programming. You can think of classes as functions which are also…


When we create a new Rails project, we are able to use ActiveRecord to validate our data. In ActiveRecord, validations are special methods that prevents “bad data” or invalid data from being persisted into a database. When we write programs and web applications, we build them with others in mind. We can expect that other users use our programs and applications. However, we cannot determine how these users will interact with the program. Users may or may not try to insert invalid data into our database. If invalid data is added to our database, this can cause a lot of…


The start of a wonderful friendship.

When I first began coding, errors were my worst nightmare. There were countless times where I would confidently write over 100 lines code just to get a big red error message in return. However, I soon realized that errors come naturally. And In addition to learning how to code, you have to learn how to debug your code efficiently.

Screenshot of errors after writing over 100 lines of code
Screenshot of errors after writing over 100 lines of code

At Flatiron School, you are given labs that contain tests you need to pass in order to submit your work. I relied heavily on rspec to guide me and help me pinpoint where I messed…

Karina Guerra

Salvadoreña exploring the world of coding. Petting animals and building things that help people and the environment are my two biggest passions :) Based in NYC.

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store