Double loop with map() function in Google Earth Engine

Question

In Google Earth Engine Developer\'s Guide, there is a recommendation to avoid for() loops. They recommend to use map() function as this example:

Answer 1

The easy way to do this is with a single map over the "months" you care about.

// Collect images for each month, starting from 2000-01-01.
var months = ee.List.sequence(0, 18*12).map(function(n) {
  var start = ee.Date('2000-01-01').advance(n, 'month')
  var end = start.advance(1, 'month')
  return ee.ImageCollection("MODIS/MYD13A1").filterDate(start, end)
})
print(months.get(95))

This will return a list of ImageCollections. Most months will have only 1 image, since MYD13A1 contains 16-day images, but some will have two. Month 95 is Jan of 2008 and has two.

Alternatively, you could join the collection with a collection of dates, but this is simpler.

And you should prefer filterDate over calendarRange when possible, as it's optimized.