A question that I am commonly asked by developers, especially those who are new to web development, is where to go to learn more about the tools included with Kendo UI Builder. (Javascript, CSS, HTML5, AngularJS, Bootstrap, etc.) Below are a few of my favorites. Some sites are free and other charge a small fee. Read the syllabus to understand what topics will be covered and choose a course that best suits your need and experience level.
NOTE: Progress is not affiliated with any of these sites nor warrants the service and content offered.
CourseRA - I use this site extensively. CourseRA partners with leading universities to provide low cost, on-line training. Search for the keywords "javascript:" or "web development" to see what courses are offered. https://www.coursera.org
Udemy - Offers low-cost, on-line training courses. Search for "Javascript" or "web development" to view content related to web based development. https://www.udemy.com
w3schools - Free. Offers introductory lessons on many web based technologies. (HTML, CSS, Javascript, Bootstrap, Angular, etc.) https://www.w3schools.com
So there are a few of my recommendations. What other sites or methods have been effective for you when learning web technologies?
It would be helpful to get a list of the courses you have taken from the above list, as they relate to Kendo UI Builder and the new technologies utilized in it. Think if it as sort of a 'Play List" to start off with before venturing off on our own. Of course all YMMV and "no warrants intended", yada-yada-yada, all legal issues covered...
With CourseRA, I've taken several courses that are offered by Johns Hopkins University and they've always been very solid no matter the subject. Johns Hopkins offers a web development course using CSS/HTML/Javascript. They also have a class on AngularJS, but I am not sure if the previous 4 classes from the Ruby on Rails specialization is a prerequisite or if it could be taken by itself. (You'll need to look into that.). CourseRA is my favorite vendor for on-line training and I am currently pursuing two specializations through them. (Non-KUIB related) They do offer a "try before you buy" so I'd recommend you check out the course above and see if it works for you.
W3Schools is my goto, quick lookup whenever I can't remember a specific syntax.
I haven't taken a course through Udemy for a while and the content has since changed. My experience with them was positive though.