1. Underscore

Underscore is a very useful JavaScript library that helps you with functional programming.

2. Chart.js

This is an awesome open-source JavaScript library if you want to add beautiful charts and graphs to your project.

3. Voca

Voca is one of the best JavaScript libraries for manipulating strings. It is supported on all major browsers and has over 3000 GitHub stars.

4. FullPage.js

An amazing open-source JavaScript library that helps you to easily create full-screen scrolling websites.

5. D3.js

D3.js is one of the popular JavaScript libraries that gives you the ability to easily manipulate documents using data. The library supports HTML, CSS, and SVG.

6. Ramda

Ramda is another awesome library that makes functional programming in JavaScript a lot easier for you.

7. Lodash

Lodash is a very popular JavaScript utility library that makes it easier for you to work with different data types(ex: numbers, strings, objects, and arrays).

8. Leaflet

Leaflet is another amazing open-source JavaScript library when creating beautiful mobile-friendly maps. It has more than 32.000 stars on GitHub.

9. Immutable.js

Immutable.js is a very useful JavaScript library that provides you with immutable data structures such as list, stack, map, and more.