Try www.w3schools.com although I'm sure there are better sites. Also you might want to look into some xml and DOM - it's all on the site I linked.
Honestly, I find the best way to learn something new like this is to watch Youtube videos. Not only can you follow along, but if you are struggling you can read the comments section. There's a number of really good Youtube users who have posted some fantastic tutorials on learning Javascript.
best for me is practice, want to set yourself a challenge, find a site you like and try to duplicate it, you have unlimited challenges that way
W3schools.com is the best website to learn about JavaScript. You can also find other websites and eBooks which provide you tutorials on JavaScript. Personally I start learning from W3schools and by watching videos on YouTube and after that I design and code pages. YouTube videos help me a lot. Through videos you can easily understand how and where to implement the code on your application.
Hi Florin, I recommend trying codeacademy dot com. Great for learning the basics of javascript, jquery, html, css and a number of other languages too. In my personal opinion, w3schools is not the best place to learn though other may find otherwise. In many development communities they are not fans of w3schools, and you can see evidence of that in gisthub or stackoverflow - both of those are great communities once you get started. I think the best way to learn is honestly by using it. Start a project with it immediately and you'll be surprised what you can learn just by searching. IE 'how do I do this in javascript?' Codeacademy will help you with some basic understanding of client-side coding, syntax and the DOM (document object model) which will make the rest of your learning much easier. Cheers, Kris