I've background in java swing programming with basic working knowledge of spring, javascript, angularjs, http. I want to learn web server side programming using express js. Will i need to first learn nodejs and then be able to use expressjs or starting express js directly will be possible? I'm planning on creating rest apis using express and then consuming them with angular js.
I will like to answer this question based on your past experience. Can you learn Java Swing framework without learning Java? No you can't. because you should understand concepts of Java to best use the Swing package. Similarly, you should understand the concepts of Javascript and Node.js to best understand Express Framework.
I would suggest you to start with a small project of setting up a server using express and node.js. And dig deep into node concepts whereever you face problems.