According to Wikipedia, a software framework is an abstraction in which software, providing generic functionality, can be selectively changed by additional user-written code, thus providing application-specific software, while a JavaScript library is a library of pre-written JavaScript code that allows for easier development of JavaScript-based applications, especially for AJAX and other web-centric technologies.
With JavaScript being a very powerful programming language, I’ve always wondered why there are so many JavaScript frameworks and libraries in the first place, so I decided to find out why. You see, the foundation of contemporary web development is now made up of JavaScript frameworks and libraries; it has entirely changed how web applications are created, maintained, and scaled.
In this article, we’ll take a deep dive into the history of JavaScript frameworks and libraries, analyzing the reasons for their creation and their revolutionary effect on the web development field. In the early days of web development, basic features like DOM manipulation and form validation were done with JavaScript.
However with the emergence of more complicated large-scale web applications, maintaining code, organization, and scalability came with enormous difficulties. A Structured Development approach was imperative and necessary to curb the abundance of spaghetti codebases, complex logic, and entangled dependencies.

JavaScript Frameworks & Libraries
The answer to all the issues with conventional JavaScript development approaches became JavaScript frameworks. The groundbreaking creation of frameworks like Google’s AngularJS in 2010(https://en.wikipedia.org/wiki/AngularJS) ushered Structured architecture for single-page applications (SPAs) creation into a new phase. The creation of clear, extensive, and maintainable codebases was now possible with framework-pioneered ideas like; modulization, dependency injection, and two-way data binding.

Top JavaScript Frameworks/Libraries and Their Key Features

Angular (https://docs.angularjs.org/guide)
Angular is an open-source JavaScript-based web framework for developing single-page applications (SPAs), it was developed and released by Google in 2010.
Key Features

• Angular uses a more efficient Model View Architecture (a software pattern for developing applications), which helps save time in coding.
• It utilizes a unit testing technique that allows users to create more efficient applications, it also helps to detect any mistake in each line of code.
• Users have free control over adaptability which helps to meet huge data requirements.
• It uses two-way data binding, in which the view layer of the architecture is an exact representation of the model, so any changes made at either layer reflect automatically.
• Angular also has an innate API and it is capable of reusing code to meet a particular development target.

Svelte (https://svelte.dev/docs/introduction)
Svelte is a free open-source component-based frontend framework, that was created by Rich Harris in 2016.
Key Features

• It has reactive components making it possible for developers to effortlessly create components that react to changes in their internal state or external data.
• Svelte uses a compilation approach, so it generates smaller bundle sizes for web applications, resulting in faster loading times and top overall performance.
• Svelte natively supports animations and transitions, thereby enabling developers to create visually appealing and smooth user interfaces that optimize the user experience.
• Svelte has a Component-based architecture that encourages the decomposition of UIs into reusable and encapsulated components.

Ember.js (https://guides.emberjs.com/release/)
Ember.js is an open-source JavaScript web framework that utilizes a component-service pattern, it was created by Yehuda Katz in 2011.
Key Features

• Ember.js is guided by the principle of Convention over Configuration (CoC). This means it has its own specific set of default rules and conventions that permits developers to complete tasks with less coding, therefore making the entire development process seamless and efficient.
• Ember.js has a powerful command line interface called Ember CLI. With this tool, a developer has everything he/she needs to create an Ember.js application, all together in one place. This includes a project structure, development server, testing tools and a build pipeline.
• Ember.js improves the performance of complex user interfaces with the aid of a lightweight component library called the Glimmer rendering engine. Which uses incremental rendering to quickly create the initial render, only updating the parts of the DOM which have changed.
• Another key feature of Ember.js is its strong convention of routes. It uses URL-oriented development approach where each URL corresponds to a specific object in the application.

Backbone.js (https://backbonejs.org/#Getting-started)
Backbone.js is a JavaScript rich-client web app framework based on the model–view–controller design paradigm, which is intended to connect to an API over a RESTful JSON interface. It was developed by Jeremy Ashkenas in 2010
Key Features

• It allows for much easier and seamless development of one-page applications using JavaScript functions.
• It has many distinct kinds of building blocks like routers, views, events, models, and collections for creating client-side web applications.
• It has a simple library that is used to separate business and user interface logic.
• It manages the data model including the user data, and displays this data on the server side with the same format written on the client side.

Aurelia (https://aurelia.io/docs)
Aurelia is a modern, front-end JavaScript client framework for building web, mobile, and desktop applications.Its main goals are to have the least amount of framework intrusion, leverage convention over configuration, and closely correspond with web platform specifications.

Key Features

• Aurelia allows robust reactive binding to any object. Through the use of adaptive techniques, it can select the most efficient way to observe each property in your model and automatically syncs your UI and your state with best-in-class performance.
• Aurelia has an extensive ecosystem that includes plugins like state management, internationalization and validation to enhance development.
• Unit testing is as simple as testing vanilla JavaScript because Aurelia allows you to combine modern JS modules with an unobtrusive approach, Aurelia makes unit testing as simple as testing vanilla JS.
• It provides you great extensivity by allowing you create custom elements, add custom attributes to existing elements, control template generation, customize template syntax, create new reactive binding types, and extend the DI.

React (https://react.dev/)
React is a JavaScript library for building user interfaces based on components on the front end, it was developed by Facebook in 2013.
Key Features

• It has JSX; which is a syntax extension that allows you to write HTML-like code directly in JavaScript code.
• It can be integrated easily with any application because of its use of a virtual DOM model.
• It has reusable components, which makes it easier for development.
• It uses a one-way data flow; this means data is passed from parent components to child components, which makes debugging easier.

Vue.js (https://vuejs.org/guide/introduction.html)
Vue.js is a progressive front-end JavaScript library used for building user interfaces and single-page applications (SPAs), either small or large. It was created by Evan You in 2014.
Key Features

• It utilizes data binding which helps manipulate or assign values to HTML attributes, change the style, and assign classes with the help of a binding directive called v-bind.
• It has components that have reusable codes and pre-defined options for custom elements, saving coding time in the process.
• It uses a Mobile-View-View-Mobile (MVVM) structure which separates the Graphic User Interfaces (GUI) from the model's business logic.
• Unlike other frameworks Vue.js is simpler in terms of both API as well as design, this helps web developers to build simple applications in a single day, and also create high-end SPAs with the dual integration mode.

Three.js (https://threejs.org/docs/)
Three.js is a cross-browser JavaScript library and application programming interface that uses WebGL to create and display animated 3D computer graphics in a web browser. It was created by Ricardo Cabello in 2010
Key Features

• Effects: Anaglyph, cross-eyed, and parallax barrier.
• Scenes: add and remove objects at run-time; fog.
• Cameras: perspective and orthographic; controllers: trackball, FPS, path and more.
• Animation: armatures, forward kinematics, inverse kinematics, morph, and keyframe.

Lodash (https://lodash.com/docs/)
Lodash is a modern JavaScript utility library delivering modularity, performance & extras.
Key Features

• Helper functions like map, filter, and invoke.
• Function binding.
• Javascript templating.
• Deep equality checks.

Moment.js (https://momentjs.com/docs/)
Moment.js is a JavaScript library that is used to parse, validate, manipulate, and display dates and times in JavaScript
Key Features

• Moment.js allows to parse date into the desired format using parsing. This is possible in the string, object, and array formats.
• With Moment.js we use inbuilt methods to manipulate the Date and Time on the moment
• Developers can perform date validation using the isValid() method provided by Moment.js. It also has various parsing flags to validate dates.
• It has a number of built-in techniques to determine whether the date is larger or less than the supplied input.

Reasons for These Frameworks and Libraries
There are other reasons for the creation of JavaScript frameworks, each of them further emphasizing the need for organized development, and they include;

Optimized Developer Productivity
With the emergence of JavaScript Frameworks, common problems encountered by developers like routing, state management, and user interface rendering now have pre-made solutions by abstracting away the tediousness of recurring operations, thereby accelerating productivity and freeing up developers to focus on creating novel features and functions.

Improved Code Organization
A prescriptive architecture that encourages code structure and concern separation is favored by frameworks through Model-View-Controller (MVC) or Model-View-View-Model (MVVM). This is a modular approach that allows the codebase to be more naturally resistant to entropy, making it easier to navigate, understand, and work on together.

Cross-Browser Compatibility
The complex differences between different browsers can prove to be an issue for developers but JavaScript frameworks protect developers from that. They also provide a consistent user experience across different browser settings by embedding browser-specific quirks and providing polyfills for experimental capabilities, showing that there’s no need for tedious browser-specific workarounds.

Community and Ecosystem
Their technical capabilities are not the only selling points of JavaScript frameworks, but also the lively communities and ecosystems that surround them. These communities and ecosystems have tools, plugins, and libraries, which in coexistence with the frameworks optimize the development process with a plethora of resources, documentation, and community assistance.

Development of Single Page Applications (SPAs)
The emergence of JavaScript Frameworks has made the creation of dynamic and responsive SPAs possible; now, content does not need full page reloads instead it can be dynamically loaded. Vue, Angular, React, etc. are frameworks that facilitate SPA development through features like client-side routing and state management.

Data Binding
With many JavaScript frameworks and libraries offering data binding capabilities, developers are now able to establish a connection between the user interface and the application’s data model, so when there are any data changes, the user interface updates automatically to reflect the new state, so there is no need for manipulating and synchronizing the DOM manually.

Performance Optimization
Frameworks and Libraries have drastically reduced bundle sizes and improved loading through code splitting, lazy loading, and tree shaking. Also, they have improved initial page load speed and search engine optimization (SEO), by leveraging server-side rendering (SSR) or static site generation (SSG).

Conclusion
In conclusion, JavaScript frameworks and libraries have brought a whole new dimension of features to web development, equipping the modern developer with the necessary tools to create better web applications more efficiently, thus ensuring further advancement and the possibilities of an era with incredible potential.