Project Start Date: 21/06/2021

Introduction

I'm currently a 4th year student studying a double major in comp sci and game design, and soon I'll need to find myself an internship.

As of right now, doing game dev doesn't seem like the best choice for my long term career, so I'm considering web dev as another option I can go down.

I've just applied for a web dev internship, and I realized React.js is a popular framework that a lot of places use in their work, yet I don't know anything about it. All this time I've only been building web apps "raw", and it seems so inefficient now that I've got exposed to the kind of stuffs React can do.

So, I'm doing this partly because I wanna prepare myself for the web dev internship in case I do get it, but I also wanna expand my skills and knowledge as a web dev in general.

And so, this is the start of my React.js learning journey. From here down will be a log of questions, answers and discoveries that I've noted down along the way.

Study Log

Day 1: 21/06/2021

Lesson 0: About React

Resources:

• freeCodeCamp.org: React JS Crash Course 2021
• C#Corner - What And Why React.js

Notes:

This is basically coding in C# for Unity.

• There is a component system of a sort. Eg. You can have a 'Header' component, a 'Body', and a 'Footer' component, each being a separate script on their own, and can be modular (you can choose to have or not to have them in the app, or even pass them as parameters).
• There seems to also be a central location, like a main() function (looks like it's <App /> for React) where everything falls into place.
• return seems to be the "renderer" for the web app.
• There seems to also be a "central" renderer as well:

reactDOM.render(<App />, document.getElementById("root"));

Conclusion: This is so much more efficient since I've always been building web apps "manually", which meant having to deal with only a massively confusing tree of nested tags. Whereas this allows me to break it down into an easier-to-understand structure. This might also be faster than typing the tags out manually too?

Apparently, React.js is also:

• Easy to learn
• Performant
• "Super easy to test"
• "Super reusable (in terms of code)"

I'll keep these things in mind as I'm going through this to see if these are true or not

---

Lesson 1: Installing React

Resources:

• freeCodeCamp.org: React JS Crash Course 2021
• MOSH: React JS - React Tutorial for Beginners

Notes:

• This is done via command prompt.
• The videos I watched recommended to install it in the project folder, not in like C:/Programs or anything "global"
  • This makes it seems like the installing process needs to be repeated for every new project.
  • This is less than ideal for me since I'll be making many web apps, which might turn into many separate projects.

Questions:

❓ Q1: Can I just make a "default" project with this installed and just copy pasta every time I make a new project?

🤔 Theory: It seems faster that way, though I guess the downside is it won't be 100% up to date if I make a new project say 3 months down the line for example.

❗ A1: There is a better way answered in A2.

❓ Q2: What about putting every React-based projects inside a "master" folder called something like React Web Apps?

🤔 Theory: This might not work in a professional environment where each project needs to be kept separate (I actually don't know why but I feel like it's a good idea), but it might work for my purpose cuz it might save lots of time from having to reinstall pretty much the same package for every.single.project that I'll be making pretty much rapidly.

❗ A2: Yes you can. Just install React like normal, but put every project in their own folder under the src folder. Then make an index.js in the src folder. That will be the "main" function that renders everything. In order to still have a "pseudo main" function for each project, make an App.js where everything is organized. Also, an added bonus to this is if you wanna update React for every project, just reinstall React and copy pasta the src folder over.

Discoveries:

• After trying to compile HelloWorld for Lesson 2, it looks like you'd have to reinstall it for every project. Command Prompt is complaining about not being able to find index.js, which there can only be 1 in src folder, but I need to have multiple for each project.
• Exceeeept, this part says I can. So I'm gonna try it (Update: IT WORKED)
  • Putting index.js in the src folder made this modular thing so much more apparent. If I wanna test a project, just pass that project's "main" function in the renderer statement (React is so powerful).
  • Downside to this is, I can't stick to the convention of naming the self-enclosing tag for the main renderer the same name as its path, because every "main" script for every project would be named App

---

Lesson 2: Hello World

Resources:

• About JSX
• About the root element
• Discussion about only putting JSX in .js files

Notes:

• Reminder to always do this before writing anything:

import React from "react";

• To do the main render, do:

import ReactDOM from "react-dom";
reactDOM.render(<h1>Hello World</h1>, document.getElementById("root"));

• The html-like tags are actually in JSX
• Rules for JSX tags:

There can only ever be 1 enclosing tag. If you wanna have multiple adjacent you'd need to enclose it in a <div> tag. Example:

<div>
	<h1>Hello World</h1>
	<p>This is a paragraph</p>
</div>

• Do npm start in the src folder to start compiling.
• You can quick access the src folder in cmd or shell by shift + right click > Open PowerShell/Command Prompt here.
• Do ctrl + C to stop.

Questions:

❓ Q3: I wanna know where this "root" is when doing getElementById. It's probably not important to know, but when I have time to come back I wanna check this.

❗ A3: So apparently according to this, the root element provides the methods necessary for rendering the components in the React web app.

❓ Q5: What is JSX?

❗ A5: According to the official docs, JSX is a syntax extension to Js (not actually Js the language) used alongside Js in developing React apps. It acts as a language that handles the UI side of the app while Js will handle the logic side of the app.

---

Lesson 3: Implementing Components

Resources:

freeCodeCamp.org: React JS Crash Course 2021

Notes:

• Always have a folder named components that contains all the component scripts.
• Always also write export default [FunctionName] for every component file.
• Always also also have an App.js file for a main function.
• Remember to import the components before using it.

---

Day 2: 22/06/2021

Exercise 1: Making a Todo list

---

Lesson 4: Styling with React

Resources:

freeCodeCamp.org: React JS Crash Course 2021

Notes:

• Where you'd normally use class for an html tag (ie. <div class="something">), replace it with className.
• Right now, just worry about doing this for the React elements (html-like tags). Don't worry about the components just yet.
• Everything Most of what you'd normally do in css is kept the same.
• Property names are always in camelCase.
• They also need to be an object (ie. surrounded by { }).
  • Therefore, if you wanna write inline styling, it'd be {{}}. First pair to "convert" to Js, second pair to declare the object.

---

Lesson 5: Javascript in JSX

Resources:

freeCodeCamp.org: React JS Crash Course 2021

Notes:

• If you wanna do Js stuffs in the middle of a JSX statement, just put { } around it.

Eg.

<h1>Hello {fName + " " + lName}!</h1>

---

Day 3: 24/06/2021

Lesson 6: Properties (Props for short)

Resources:

freeCodeCamp.org: React JS Crash Course 2021

Notes:

• Think of this like object properties in Unity.
• The script for a component can be thought of like a "constructor" of a sort to pass data in when creating new instances of the object.
• Only need 1 pair of { } when referencing data because it's not an object.
• If an object is passed into the function instead of raw data, then you'd need to call parameter.object.variable. Calling parameter.variable would only work if you didn't pass data in as an object (which you shouldn't anyway).

Questions:

❓ Q4: Do we need to specify the data type when passing values like this.

🤔 Theory: It looks like we don't need to specify data type like int a = 10 when doing this. Though I guess if it doesn't fit it would just not compile.

❗ A4: What was said above.

---

Day 4: 25/06/2021

Day 5: 11/07/2021

Day 6: 12/07/2021

Lesson 7: Map

Resources:

Official documentation for Js Map

Notes:

• In order to turn "raw data" (eg. imported from a .json) into components for React, we need to use "high order" array functions (array manipulation functions).
  • They allow you to "do things" for each element in the array.
• Map is an example. It creates a new array where each element is applied a function that was passed in as the parameter for the map function.
• Example: This code will double each element in the nums array.

const nums = [1, 2, 3, 4];
const doubled = nums.map((nums) => {
	return nums * 2;
});

• For React, it would look like this

const components = someDataSet.map((data) => {
	return <Component data1={data.data1} data2={data.data2} />;
});

• Good for passing data of objects with repeated elements (eg. lists) to the return function.
• Reminder to import the object first before using.
• Some other array manipulation functions that might be of interest:
  • filter
  • sort
  • reduce
  • every
  • some
  • find
  • findIndex
• Reminder: You can return the entire array without having to repeat code. Example:

in index.js

...
return (
    <div>
        {components}
    </div>
);
...

• Reminder #2: Your data needs to be exported in order to be used.

---

Day 6: 12/07/2021

Day 7: 17/07/2021

Lesson 8: Class-based Components (vs Functional Components)

Resources:

freeCodeCamp.org: React JS Crash Course 2021

Notes:

• Functional components is what I've been doing for the last how many projects.
• Class-based components is just superior cuz
  1. The function that I've been using is inside of a class component
  2. Class components are a lot better cuz it allows for state(?) and many other things.
• A class would 99.99% always extends React.Component.
• If it will have the rendering function, make sure it's inside the render() method.

Exercise: Convert all functional components into class-based components.

Questions:

❓ Q6: Is there an occasion where we would use functional components over class-based components?

🤔 Theory: I know class-based is superior, but it feels unnecessary having to type extra lines when you don't even use it. I guess if you don't need to use the React.Component's functions then you don't need it.

---

Day 7: 17/07/2021 Day 8: 19/07/2021

Lesson 9: States

Resources:

• freeCodeCamp.org: React JS Crash Course 2021
• learn.co: React Updating State

Notes:

About states:

• Can be maintained by a component (has to be class-based) and can be changed if need to.
• To have states, you need to have a constructor.
  • Inside the constructor you need to call super() in order to use related function to intialize states.
  • You can initialize states inside this.state = { }.
  • All of this can be done automatically by typing rcon to access the code snippet.
• Neat thing about states is if you change it, it'll automatically update for every child component that uses it.
• Note: variables are declared as variable: value NOT variable = value.

To change states:

• Use this.setState(). There are 2 ways to pass things into setState():
  • An object literal (eg. {aRandomProperty: "someValue"}).
  • A function that returns an object literal. This allows us to access the old version of the state. (VERY IMPORTANT TO KNOW)

  this.setState((prevState) => {
  	return {
  		someNumber: prevState.someNumber + 1,
  	};
  });

• Reminder that you'll need to bind whatever function has setState() to this in the constructor.

this.ThisFunction = this.ThisFunction.bind(this);

• Whenever a state changes, React will update it for every component that uses it.

---

Day #

Lesson #: Copy Pasta Template

Resources:

Notes:

Questions:

❓ Q1:

🤔 Theory:

❗ A1: