function for converting labelled gmail emails to a spreadsheet

getEmails.js

function getEmails() {
  // set spreadsheet and retrieve labels
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var name = "LABEL";
      // create sheets and clear content
      var label = GmailApp.getUserLabelByName(name);
      var sh = ss.getSheetByName(label.getName()) || 
      ss.insertSheet(label.getName(), ss.getSheets().length);
      sh.clear();

      // get all messages
      var eMails = GmailApp.getMessagesForThreads(
        GmailApp.search("label:" + label.getName()))
          .reduce(function(a, b) {return a.concat(b);})
          .map(function(eMails) {
        return eMails.getFrom() 
      });

      // sort and filter for unique entries  
      var aEmails = eMails.sort().filter(function(el,j,a)
        {if(j==a.indexOf(el))return 1;return 0});  

      // create 2D-array
      var aUnique = new Array();  
      for(var k in aEmails) {
        aUnique.push([aEmails[k]]);
      }

      // add data to corresponding sheet
      sh.getRange(1, 1, aUnique.length, 1).setValues(aUnique);
}