4.3. Using an ISO Formatted Date for Document IDs

The ISO 8601 date standard describes a useful scheme for representing a date string in a Year-Month-DayTHour:Minute:Second.microsecond format. For time-bound documents in a CouchDB database this can be a very handy way to create a unique identifier, since JavaScript can directly use it to create a Date object. Using this sample map function:

function(doc) {
  var dt = new Date(doc._id);
  emit([dt.getDate(), doc.widget], 1);

simply use group_level to zoom in on whatever time you wish to use.

curl -X GET "http://localhost:5984/transactions/_design/widget_count/_view/toss?group_level=1"


curl -X GET "http://localhost:5984/transactions/_design/widget_count/_view/toss?group_level=2"


Another method is using parseint() and datetime.substr() to cut out useful values for a return key:

function (doc) {
  var datetime = doc._id;
  var year = parseInt(datetime.substr(0, 4));
  var month = parseInt(datetime.substr(5, 2), 10);
  var day = parseInt(datetime.substr(8, 2), 10);
  var hour = parseInt(datetime.substr(11, 2), 10);
  var minute = parseInt(datetime.substr(14, 2), 10);
  emit([doc.widget, year, month, day, hour, minute], 1);