Interactivity with JavaScript | Coursera --https://www.coursera.org/learn/javascript
This course will introduce you to the basics of the JavaScript language. We will cover concepts such as variables, looping, functions, and even a little bit about debugging tools. You will understand how the Document Object Model (DOM) is used by JavaScript to identify and modify specific parts of your page.
JavaScript | Mozilla Developer Network --https://developer.mozilla.org/en-US/docs/Web/JavaScript
JavaScript (JS) is a lightweight, interpreted, programming language with first-class functions. Most well-known as the scripting language for Web pages, many non-browser environments also use it, such as node.js and Apache CouchDB. JS is a prototype-based, multi-paradigm, dynamic scripting language, supporting object-oriented, imperative, and declarative (e.g. functional programming) styles.