I'm currently looking for a way to make node.js-API-calls from static html. I've looked at Express and similar template engines, however they would require me to write my html and generate it from their template engines instead of the other way around. I often get production ready HTML from designers and don't want to rewrite that to fit with express. Alternatively is there a converter from existing .html to template engines?
To get a bit more basic, I want to use node.js in a similar way to ajax, basically being able to call things like <img onClick="someNodeFunctionWithDatabaseCalls()"> from an html-file running on node as a server and then manipulate the .html-file with DOM or something like that. Is there a way to do that?
Node.js is for server-side scripting only. In order to run node.js code in response to an event on your webpage, you will have to use websockets to send a request to your server, which can in turn run the necessary code (db requests, etc.).
As far as various web sockets go, I would recommend using socket.io; it is very simple to use, and is well known for working on many different devices. See socket.io for more information and examples.