NodeJs instead of Apache

I have a website under domain (say example.com) which is hosted on Amazon Web Services EC 2 instance which has Apache already installed and ready to run on port 80.Now I wish to transfer from Apache to node JS (where Node JS runs on another port, say 8001).How to change the HTTP port address of EC 2 say that when i go to that URL (example.com) it should run on node JS instead of Apache (While for temporary,node JS runs on example.com:8001). How is it possible and Kindly help?

So you cannot direct a standard web address (e.g. www.example.com) to anything other than port 80. By default http is on port 80 and https is on port 443. You can override that default by explicitly giving the port but you cannot change that default.

So your options are:

Replace Apache with Node on port 80. This will involve shutting down Apache (and making sure it doesn't auto restart on reboot), and changing your node port to port 80. This also will probably require running your node service as root (as port 80 is usually protected) and this is not recommended (Apache starts as root to get the port but then usually immediately switches to non-root user).
Have Apache proxy forward requests to Node. This means Apache is still your main webserver and listens on port 80 but certain requests are sent on to Node.

This second option could be done using mod_proxy with config like this:

 ProxyPass "/foo" "http://localhost:8001/"
 ProxyPassReverse "/foo" "http://localhost:8001/"

It all depends on what you want to use your set up for and making best use of the software available to you.

Typical set up is a multi-layered approach involving one or more of these:

LoadBalancer (optional for high load sites or where resiliency is key)
Webserver
Appserver
Database

Yes you could use just Node for all of these layers. However, to me, it is more an application server than a webserver.

A webserver like Apache or Nginx is specifically designed to act like a web server, and by that I mean serving static pages and doing other top layer stuff. They have several features built up over their years to provide speed and security. Now nearly everything they can do, can be done in Node but not quite as easily and not by standard and often requires pulling in 3rd party modules.

A webserver then typically offloads dynamic work to other programs. This could be scripts (PHP or Perl), or separate app servers like Tomcat, Jboss or Node. These are typically very good at specific tasks (e.g. talking to database and generating dynamic pages) but less good at severing static pages quickly.

The beauty of node to me is for micro- services, where you can have lots of independent, but potentially interlinked, node services which are all lightweight and good at one task and the web server is still needed in front of them. This compares to a bulky multi-tasking J2EE server like Tomcat or Jboss that you would use in the past which tried to do every dynamic app under one process (though admittedly often under separate WAR files).

So, without knowing your full use case, I would suggest Apache and Node instead of Node replacing Apache.