The following texts are freely available online:
- ECMA-262: ECMAScript 2017 LANGUAGE SPECIFICATION, 8th Edition, at www.ecma-international.org/ecma-262/8.0/. This provides the official standard to the current version of JS
- ELOQUENT JAVASCRIPT, 2nd Edition, by Marijn Haverbeke, at http://eloquentjavascript.net/.
- EXPLORING ES6, by Dr. Axel Rauschmayer, at http://exploringjs.com/es6/.
- EXPLORING ES2016 AND ES2017, by Dr. Axel Rauschmayer, at http://exploringjs.com/es2016-es2017/. This text will let you get up to date with the latest features in JS.
- FUNCTIONAL-LIGHT JAVASCRIPT, by Kyle Simpson, at https://github.com/getify/Functional-Light-JS.
- JAVASCRIPT ALLONGÉ, by Reginald Braithwaite, at https://leanpub.com/javascript-allonge/read.
- PROFESSOR FRISBY'S MOSTLY ADEQUATE GUIDE TO FUNCTIONAL PROGRAMMING, by DrBoolean (Brian Lonsdorf), at https://github.com/MostlyAdequate/mostly-adequate-guide.
If you prefer printed books, you can go with this list:
- FUNCTIONAL JAVASCRIPT, Michael Fogus, O'Reilly Media, 2013
- FUNCTIONAL PROGRAMMING IN JAVASCRIPT, Dan Mantyla, Packt Publishing, 2015
- FUNCTIONAL PROGRAMMING IN JAVASCRIPT, Luis Atencio, Manning Publications, 2016
- INTRODUCTION TO FUNCTIONAL PROGRAMMING, Richard Bird & Philip Wadler, Prentice Hall International, 1988. A more theoretical point of view, not dealing specifically with JavaScript.
- PRO JAVASCRIPT DESIGN PATTERNS, Ross Harmes & Dustin Díaz, Apress, 2008
- SECRETS OF THE JAVASCRIPT NINJA, John Resig & Bear Bibeault, Manning Publications, 2012
Also interesting, though with a lesser focus on Functional Programming:
- HIGH-PERFORMANCE JAVASCRIPT, Nicholas Zakas, O'Reilly Media, 2010
- JAVASCRIPT PATTERNS, Stoyan Stefanov, O'Reilly Media, 2010
- JAVASCRIPT: THE GOOD PARTS, Douglas Crockford, O'Reilly Media, 2008
- JAVASCRIPT WITH PROMISES, Daniel Parker, O'Reilly Media, 2015
- LEARNING JAVASCRIPT DESIGN PATTERNS, Addy Osmani, O'Reilly Media, 2012
- MASTERING JAVASCRIPT HIGH PERFORMANCE, Chad Adams, Packt Publishing, 2015
- PRO JAVASCRIPT PERFORMANCE, Tom Barker, Apress, 2012