Angular - Summary and Link
The Angular framework is often used for Single Page Applications on a website (pages that can talk to the server and change without reloading the whole webpage). Angular uses modules of code to create applications which can make the application more efficient. Angular is nice because the code can be used on various platforms, which makes it easy to reuse your code. Angular is used by my large websites, including PayPal and Gmail. Angular is run in the browser (client). It has directives that are used to put data into a webpage and binds it with an HTML element. I found this example on the W3Schools page that showed just how easy it was to work with the DOM and user input using Angular with very little code. Recreating this with standard JS would take a lot more coding effort.
React - Summary and Link
The React framework is often used build the user interface. It can be run on the server or in the browser. React is easier to learn than some of the other frameworks. It was created by Facebook and helps to create dynamic web pages - which makes sense since that is what Facebook is all about. One reason it's easier to learn is that its markup JSX is very similar to HTML & XML. React also creates a virtual DOM that helps it perform better even when it is larger and has a lot of updates. This makes it great to use for social networks, ecommerce and mobile apps. With the virtual DOM, it allows React to only render the part of the page that is changing vs. the whole page.
Node JS - Summary and Link
The Node framework is different than some of the other frameworks because it runs JavaScript outside of the browser (on the server). Node is also an easy to learn framework. Node is fast, which makes it easy to scale to larger applications. One feature that makes it useful is that it allows your application to talk to the server but the server to also start communication with the application. Node is pretty popular because it has a large open source library and is very compatible. It is used by sites like ebay, LinkedIn, Walmart, and Groupon.
Summary
In researching these frameworks I realized that there are a LOT of framework options out there for Javascript. I didn't really have a good idea prior to this of what these were or how they were used. But after seeing a few examples of each in action and reading what they do, I can see how powerful they can each be for their specific applications. The frameworks can be very time saving to a programmer and in addition to faster programming, they also offer efficient processing because they are created for the best performance for their application. Now the question is, which is the most useful to learn first? :)