You Don't Know JS and Eloquent JavaScript are one the best free books about JavaScript. For intermediate-advanced topics - Programming JavaScript Applications by Eric Elliott is a great choice.
If you like watching video tutorials - egghead.io - the content there is phenomenal! ES6, Fundamental JavaScript, Reactive Programming, ReactJS/Redux/Flux, AngularJs etc. Keep in mind though, that some of the content is premium, but there is a large quantity of free videos.
Meanwhile, you can check Codewars - a website for solving programming challenges. One of the supported languages is JavaScript.
Whatever you do, don't forget the most important part of your learning journey - practicing. Don't stop coding, even if you don't know the specs that well. Start a simple project and upgrade it with new functionalities every now and then. There are so many projects idea lists like programming-projects-for-n00bz, WebDevChallenge, karan's projects.
You can check @prank7's answer for additional project ideas.
Here are some more resources worth mentioning: