Converting ee.Date object to client string in Google Earth Engine?

Question

I'm trying to export all the images in an ImageCollection to Google Drive and by default name the output image with the date using format() function. However, when I try to name a export task by a date, the name in tasks is something like:

ee.String({ "type": "Invocation", "arguments": { "date": { "type": "Invocation", "arguments": { "value": { "type": "Invocation", "arguments": { "object": { "type": "ArgumentRef", "value": "_MAPPING_VAR_0_0" }, "property": "system:time_start" }, "functionName": "Element.get" } }, "functionName": "Date" }, "format": "YYYY-MM-DD" }, "functionName": "Date.format" })

Note the date values are gone and only some of the images are exported. Here's the link to the code

All I need is only a formatted string from a date object.

Is there a simpler way to export an image collection?

Answer 1

As @Kersten commented, you should use a client side loop

var size = S2VI.size().getInfo()
var S2VI_list = S2VI.toList(size)

for (var n=0; n<size; n++) {
  var image = ee.Image(S2VI_list.get(n))
  var date = ee.Date(image.get('system:time_start')).format('YYYY-MM-DD');
  date = date.getInfo();
  Export.image.toDrive({
    image: image,
    description: date,
    fileNamePrefix: date, // this is the name actually
    folder: 'EE Outputs',
    scale: 20,
    region: XiangJiang,
    maxPixels: 130000000000,
  })
};