Sometimes you need to get a data from your CouchDB in CSV format for some thrid-party application, or someone from your office need to write another report in Excel, etc, so here is the tiny pice of code that can give you a hint on how to create a list function that will export your data into CSV:

function (head, req) {
start({

    "headers": {

      "Content-Type": "text/csv"

     }

  });

send('Username, Name, Email\n');

while(row = getRow()) {

    send(row.value.username+','+row.value.email+','+row.value.metadata.name+'\n');

  }

}