JavaScript References

MDN - Simply the best language reference.
DevDocs - Search MDN comfortably. Even offline.
Simplified JavaScript Jargon - Glossary which explains all the buzzwords from the JavaScript eco system.
Functional Programming Jargon - Explains terms used in functional programming in the JavaScript context.
Modern JavaScript Cheatsheet - Helps developers with basic knowledge to get familiar with modern codebases.
ECMAScript® Language Specification - The standard JavaScript is based on. Only for very advanced learners.

Articles & Tutorials

A re-introduction to JavaScript* - Compact introduction covering types, variables, operators, control structures, functions and closures.
JavaScript.info - A modern tutorial from the basics to advanced topics with simple, but detailed explanations.
Glossary of Modern JavaScript Concepts: Part 1 - Learn the fundamentals of functional programming, reactive programming, and functional reactive programming in JavaScript.
Glossary of Modern JavaScript Concepts: Part 2 - Explains concepts like scope and closures, data flow, change detection, components, compilation, tree shaking.
Robust Client-Side JavaScript - Guide focused on writing robust code by describing possible failures and explaining how to prevent them.

*MDN offers a lot of other guides for every level of knowledge to dig deeper.

JavaScript Closures Demystified - Covering closures. From basics to use cases. Has useful comments.
Understanding Hoisting - Detailed explanation of the concept of hoisting in JavaScript.
Array operations - Covering the usefulness of Array's map, reduce, and filter methods.
Promises - Learning promises step by step.
Async/Await - Tutorial showing the advantages of consuming Promises via async functions.
Pure functions - Answers the question »What is a Pure Function?« epicly.
Using Fetch - Describes thoroughly how to use the Fetch API to receive and send data.
Chrome DevTools - Everything you need to know about the debugging tools built into Google Chrome.

Eloquent JavaScript - Covering the language and runtime specifics.
You Don't Know JS (book series) - Series of books diving deep into language.
Speaking JavaScript - In-depth guide beginning with the basics.
JavaScript Design Patterns - Classical and JavaScript specific design patterns.
Mostly Adequate Guide to Functional Programming - Excellent primer to functional programming using JavaScript.
Functional-Light JavaScript - This book explores the core principles of functional programming (FP) as they are applied to JavaScript.

Thin books which you can get through in a few days.

JavaScript: The Good Parts - Classic material which still has relevance.
The Principles of Object-Oriented JavaScript - Comprehensible, especially interesting for people with a class based OOP background.
JavaScript Enlightenment - Will solidify your understanding of the language.
Testing JavaScript Applications - A complete guide for JavaScript testing tools and techniques.

②ality - Language features and APIs well explained by author and trainer Dr. Axel Rauschmayer.
Pony Foo - Detailed and high quality posts from Nicolás Bevacqua all related to JavaScript.

== ? === ??? ...#@^% - Basic talk about type coercion and strict type comparison.
FunFunFunction - Educational plus entertaining YouTube show covering language features as well as architectural topics amongst others.
What the heck is the event loop anyway? - Awesome talk about the way JavaScript works, and a tool for exploring the callstack.
Become a JavaScript Console Power-User - Introduction to the browsers JavaScript console.
Debugging The Web - Learn state of the art in debugging using Chrome dev tools.
JavaScript 30 - 30 video tutorials to build neat little things with just plain JavaScript.

Promises Are So Passé - Talk that shows where async goes next, why it matters, and what you need to do to put it into practice today.
Learning Functional Programming with JavaScript - Talk containing the best explanation of map/reduce.
Understand JavaScript's this Keyword in Depth - 18 minutes divided into 8 short videos to wrap you head around this.

Codeacademy - Fundamentals of JavaScript.
Udacity JavaScript Basics - They also offer more advanced courses.
Code School - From Basics to Best Practices. Different courses related to JavaScript.
Functional programming - Learn basic principles of functional programming in an interactive way by using map, filter, concatAll, reduce and zip.
Learn JavaScript Online - Interactive JavaScript course with spaced repetiton flashcards app.
Exercism JavaScript Track - Exercism provides individual practice and mentor-based learning for free.

Exploring ES6 - Good introduction with in-depth chapters.
Exploring ES2016 and ES2017 - Follow up of »Exploring ES6«.
Setting up ES6 - Explains how to set up ES6 projects that are transpiled to ES5.
ES6 Overview - Bullet point overview including in-depth articles.
ES6 Katas - Learn ES6 by solving unit test online.
Practical ES6 - eBook with practical examples and advices.
30 seconds of code - Useful ES6 snippets that you can understand in 30 seconds or less.
What’s the difference between JavaScript and ECMAScript? - Clears the confusion about ES6 and Javascript.

DOM Enlightenment - A whole book about how to access an manipulate the DOM without a library.
You Might Not Need jQuery - Get plain JavaScript code snippets (and see their jQuery equivalents).
Traversing the DOM with JavaScript - A tutorial featuring native methods to traverse the DOM.

The Art of Node - Introductory tutorial covering the basics.
NodeSchool - Interactive self guided workshops you can also do on your own.
Node Patterns - Short books about code and networking patterns related to Node.js.
Learn Node - A premium training course to learn to build apps with Node.js, Express, MongoDB.