ng-csv omit headers for empty data

Question

I have a JSON to be exported as CSV by using ng-csv. Data looks like this:

{
   [a: 1, b: null, c: '', d: undefined, e: 5], 
   [a: 2, b: 3, c: '', d: null, e: 5], 
   [a: 5, b: 4, c: '', d: null, e: 5]
}

and directive is used like this:

<a class="btn btn-default btn-xs" ng-csv="exportToCsv()" lazy-load="true" csv-header="['a', 'b', 'c', 'd', 'e']" filename = "exported_data.csv"><i class="glyphicon glyphicon-download"></i></a></span>

Function exportToCsv is using promise to return data but I don't know which properties will have values. For example json my csv should look like this:

Q: How can I omit fields and headers for properties that are undefined, null or empty string? Can I set headers after the data is received?