How do I save text to an external file

I'm trying to create an app where whenever someone types some text into a text box a presses 'save' the text is added to a .txt (or other text file) file stored on a server/my computer (i may use the Node WebKit to create an offline version)...

I'm pretty sure this is possible but having trouble finding the solution anywhere... Can anyone point me in the right direction please?

Many thanks...

Having spoke to another user it would appear that this is possible when using the Node-Webkit function. I'm going to explore that this week but if anyone could explain the process in more detail I'd really appreciate it!

Success, it would seem once you add the node web kit as an object you are then able to use the command "append file".

I tried it with a .txt file and it worked. I'm not sure what other file types are supported...