What is server-side Javascript? Can I replace PHP applications with applications written with server-side Javascript? If this is possible, does ExtJS support server-side Javascript?
what is server-side javascript ?
Program code running on a server that happens to be written in JS.
can it replace php with server-side javascript?
Yes
if it exists do extjs has serverside javascript ?
ExtJS is a UI library, it doesn't do anything that would be all that useful server side.
You might be able to get some use out of it (little bits of it) in a similar fashion to this approach used to use YUI on the server: http://www.yuiblog.com/blog/2010/04/05/running-yui-3-server-side-with-node-js/