I want to allow user to be able to edit office documents online within the web application.
I have come to know that I can do it easily by installing Web App Server
But it requires a separate isolated server for installing it. Or I need to install it on virtual machine.
I was wondering if is there any api available (which already have Web App Server installed on it), which I can use directly with my web application to fulfill my requirement?.
The web-based Office document editing is achieved by implementing MS-WOPI protocol. The protocol consists of three parties - a WOPI Server (app serving the files...typically your app or SharePoint), a WOPI Client (Office Web Apps) and a client browser.
Unless you want to implement your own WOPI client (which should be possible but I haven't seen anyone trying to go that path) you have to use Office Web Apps or its younger brother Office Online Server.