Intro to ReactJS

Definition/Overview: ReactJS was developed by Facebook (now Meta) as a client-side JavaScript (JS) library. It is utilized by developers to build single-page apps and customize interactive user interfaces (UIs) via highly reusable and flexible web components. The relatively light learning curve (in comparison to a heavier JS framework, such as AngularJS) of ReactJS assists in optimizing UIs and their associated User Experience (UX) potential.

ReactJS also utilizes a JavaScription syntax extension known as JavaScript XML, or 'JSX'. It combines JS and HTML scripting within individual files.

Table of Contents:

1. 'Hello World' Code Example
2. Components and Elements
3. Optimization and Pitfalls
4. Supplemental Resources

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1. 'Hello World' Code Example

// projects/HelloWorldApp.jsx
import React from 'react';

function HelloWorldApp() {
  return (
    <div>
      <h1>Hello World!</h1>
    </div>
  );
}

export default HelloWorldApp;

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2. Components and Elements

What exactly are 'components'?: A ReactJS component is a piece of code that can be reused throughout an application. There are many possibilities for what ReactJS components can be--buttons, textboxes, and text headings, for example. This reuse of code slices allows for apps to be developed quicker and perform faster.

What about 'single-page apps'?: Simply put, these are apps in which clicking on elements, such as navigation menu items and various links, does not result in reloading of the app as a whole. Instead, the only reloaded content is the body of the freshly requested section. For an example of this, consider a movie and/or television streaming service, such as Hulu or Netflix. The use of a single-page app system allows for users to watch their streaming media content without reloading entire pages.

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3. Optimization and Pitfalls

How is ReactJS Optimized?: Some of the ReactJS features and techniques that benefit UI/UX developers include...

• Debouncing and Throttling
  • This limits when functions execute, and how often.
• Functional Pattern Adherence
  • This assists in handling complex code/logic, potentially reducing errors and increasing performance.
• Lazy Loading
  • This limits component loading to only when it is needed.
• List Virtualization
  • This limits the rendering of list items to only when they are available on screen to users.
• Memoization
  • This caches responses for future re-use, increasing performance when serving clients web assets.
    • Consider using memoization tools such as useMemo and React.memo.
• useReducer() and useTransition() Hook Leveraging/Utilization
  • useReducer() defines how states are to be updated.
  • useTransition() limits updates until when they are needed, potentially increasing performance.

Common Mistakes in ReactJS Development include:

• Forgetting to Use Keys in Lists
  • Keys detect added, modified, and removed items.
• Imprecise Component Structure
  • If logic is spread across components, updating/maintaining components and component reuse can become a mess.
• Mutating State Directly
  • This can cause errors and other unintended behaviors. Thus, it is better practice to update state immutably.
• Overlooking Performance Optimization Techniques
  • This includes the principles outlined in the above section.
• Overreliance on Inline Functions
  • This can cause extraneous rerendering, and therefore unnecessary performance costs.

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4. Supplemental Resources

• Intro to MERN and MEAN Stack Overview Guide
• JavaScript Event Handling Guide

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TODO: Add comparison of ReactJS to AngularJS and Next.js.