Refactoring nested example to pure functions

gistfile1.js

Y.io.xhr = function (uri, options) {
    options = options || {};

    return new Y.Promise(function (resolve, reject) {
        var io = Y.io(url, {
            // reference options directly to avoid insertion of unwanted options
            // into Y.io()
            method: options.method,
            data: options.data,
            headers: options.headers,
            form: options.form,
            timeout: options.timeout,
            on: {
                success: function (id, response) {
                    resolve(response);
                },
                failure: function (id, response) {
                    reject(response);
                }
            }
        });

        // expose abort. It is not a prototype function so it's ok to copy it
        this.abort = io.abort;
    });
};

Y.io.getJSON = function (url, options) {
    var promise = Y.io.xhr(url, options);

    return Y.mix(promise.then(function (xhr) {
        return Y.JSON.parse(xhr.responseText);
    }), {
        // pass around the abort function
        abort: promise.abort
    });
};

var getData = (function () {
  function fetchData(offset) {
    return Y.io.getJSON('/foo' + offset);
  }
  
  function concatData(dataset, offset) {
    if (dataset.length < 100) {
      offset += 100;
      return fetchData(offset).then(function (newDataset) {
        return concatData(dataset.concat(newDataset), offset);
      });
    } else {
      return dataset;
    }
  }
  
  return function getData(offset) {
    return concatData([], offset);
  };
}());