How get average recording time to the database by javascript

Question

I can get time of one operation insert to database, but I have problem to get time for 1000 operations. I get end time in the function to call when the request is sent successfully.

var startTime = 0;
var endTime = 0;
function func(){
  startTime = new Date();
  tx.executeSql('INSERT INTO tblDemo ('
                + 'personName, personAge, personColour)'
                + 'VALUES (?, ?, ?);'
               , [name, age, colour], querySuccess, errorHandler);
  setTimeout(function(){
     var result = endTime-startTime;
     alert(result);
  }, 10000);
}
function querySuccess() {
    endTime = new Date();
}

I can't use loop in this code, because operations are executed asynchronously and I can't get end time after 1000 operations.