You can use
var str = JSON.stringify(object)
to serialize your objects to a JSON string and
var obj = JSON.parse(string)
To read it back as an object. The string can be written to file. So, for example an object like this:
var p = new Foo();
p.Bar = "Terry"
var s = JSON.stringify(p)
// write s to file, get => { "Bar" : "Terry" }
// read s from file and turn back into an object:
var p = JSON.parse(s);
Writing and reading to/from files is covered here: http://nodejs.org/docs/v0.4.11/api/fs.html#fs.write