An example invocation of op.visitSubs in Fargo Scripting (http://docs.fargo.io/fargoScripting) to run in the JavaScript console in context of a Fargo.io outline to understand how op.visitSubs works.

fargo_io_op_visitSubs_starter.js

op.visitSubs ( //get bodytext
        function (headline, levelnum) { // lineCallback
            console.log("lineCB -> headline, levelnum: " + headline.getLineText () + ", " + levelnum);
        },
        function (levelnum) { // indentCallback
            console.log("indentCB -> levelnum: " + levelnum);
        },
        function (levelnum) { // outdentCallback
            console.log("outdentCB -> levelnum: " + levelnum);
        }
    );