A jQueryOnline CoursesALISONCodecademyTreehouseBootcampsRefactorUModernizrModernizr makes it easy to

A Quick Guide to Learning JavaScript LibrariesJavaScript programming is arguably the most valuable tech skill in existence. Roughly 90% of websites rely on it for browser interaction and the keyword “JavaScript” appears more on career sites than any other programming language.Learning general JavaScript is an essential part of a front-end development career, but it takes more than that to completely master the language. Approximately 70% of websites use one of JavaScript’s many libraries — sets of pre-written JavaScript code programmers can call on to allow easier development of JavaScript-based applications. These libraries are valuable skills in and of themselves (and remember they are different than frameworks).The only problem?  There are way too many of them to learn (more than 50, although it’s hard to keep count; new ones keep springing up and definition issues). You’ need to pick and prioritize depending on your career goals and the kind of development you want to do.This guide will help you do just that by describing the purpose of each library and offering some quick resources for how to learn it online.Editorial Note: These resources are mostly geared towards intermediate level learners with some advanced exceptions. You should have basic knowledge of frontend development and JavaScript before attempting to learn most of these libraries.The Most Valuable LibrariesjQueryjQuery is the most valuable JavaScript library because you can find it in 62% of websites and it is the JavaScript library of choice 95% of the time. It mostly makes the following things much easier by using an API that works across multiple browsers: HTML document traversal and manipulation, event handling and AJAX.Where to Learn:BlogsOfficial jQuery BlogLearning jQueryOnline CoursesALISONCodecademyTreehouseBootcampsRefactorUModernizrModernizr makes it easy to write conditional JavaScript and CSS, which is useful for doing work where conditions vary from browser to browser. It’s great at detecting features so you can do more of what programmers call “progressive enhancement.”Where to Learn:Udemyscript.aculo.usIt might not have a cool name like Modernizr, but script.aculo.us has still made its mark with companies and organizations including NASA, Apple and IKEA. It works well with the Prototype framework and has tools such as animation frameworks, drag and drop code options, AJAX controls, DOM utilities and unit testing. Don’t know what any of these things are? If not, maybe it’s time to learn.Where to learn:lynda.comBackbone.jsBackbone.js delivers on its name by giving web applications a stronger structure and connecting to any existing APi via a restful JSON interface. It does this by providing models with key-value binding and custom events, collections with a multi-functional API and views with declarative event handling. Again, you’ll have to dive into learning the library before you can understand these terms in a concrete way.Where to Learn:Code Schoollynda.comPluralsightUdemyUnderscore.jsThe official Underscore.js website describes it as the answer to the question: “If I sit down in front of a blank HTML page, and want to start being productive immediately, what do I need?” Underscore.js provides more than 100 functions to support crucial programming helpers such as map, filter, and invoke. It works excellently with jQuery and Backbone, meaning you should definitely learn it if you decide to tackle Backbone (jQuery goes without saying because it’s become essential for any JavaScript developer).Where to Learn:lynda.comPluralsightD3.jsThe aptly named D3 (Data-Driven Documents) is a tool for manipulating data-based documents by using frontend programming. It’s all about visualizing the data so it becomes more useful and accessible.Where to Learn:Frontend MastersPluralsightUdacityReactFacebook and Instagram teamed up to create React, a JavaScript library designed for building user interfaces. React works well with model-view-controllers MVCs and Node.js, a popular JavaScript platform.Where to Learn:BlogOnline CoursesPluralsightTuts+To become a true JavaScript master, your next step will be tackling JavaScript frameworks, which can include libraries or at least work with them. People often conflate frameworks and libraries, so remember that libraries are static collections of functionalities you can draw upon for various tasks while frameworks are a fluid set of tools — which sometimes include libraries — that almost act as applications on their own and can be modified to suit specific goals.