foo.js

const _ = require('lodash');
var foo = {
  ReportList: {
    Report: [
      {
        Graph: [
          {
            $: {
              title: 'something',
              graphtype: 'something'
            }
          },
          {
            $: {
              title: 'something',
              graphtype: 'somethingelse'
            }
          }
        ]
      },
      {
        Graph: [
          {
            $: {
              title: 'foobar',
              graphtype: 'something'
            }
          },
          {
            $: {
              title: 'foobarbaz',
              graphtype: 'baz'
            }
          }
        ]
      }
    ]
  }
};

function collectGraphTypes(reportDefinition) {
  var allGraphTypes = [];
  _.each(foo.ReportList.Report, function(report) {
    _.each(report.Graph, function(graph) {
      allGraphTypes.push(graph['$'].graphtype);
    });
  });

  allGraphTypes = _.uniq(allGraphTypes);
  return allGraphTypes;
}

function getGraphTypeDefinitions(graphTypeList) {
  return new Promise(function(resolve, reject) {
    var promises = [];
    _.each(graphTypeList, function(graphType) {
      promises.push(fetchGraphType(graphType));
    });
    Promise.all(promises).then(
      function(value) {
        resolve(value);
      }
    );
  })
}

function fetchGraphType(graphType) {
  return new Promise(function(resolve, reject) {
    setTimeout(function() {
      resolve({ newType: graphType });
    }, 1000);
  });
}
var graphTypes = collectGraphTypes(foo);
getGraphTypeDefinitions(graphTypes).then(
  function(allDefs) {
    console.log('done!', allDefs);
  }
);