Google Earth Engine - Set Null values as zero and take the mean

Question

I am trying to set the null values of NDVI to zero for districts in Indonesia. However, when I export the table, the mean value for all districts come up as zero, which is not correct. Is there a way to correctly export the mean value for all districts, whilst setting the value of null to be zero? Here is my attempt at the code:

  var districtsindo = shp4.select('NAME_3'); 



 var water_district = Ndvi.reduceRegions({
  collection:districtsindo,
  reducer:ee.Reducer.mean(),
  scale:30, 
})  


function removegeo(feature) {
 var meanvalue=feature.get('mean')
 if (ee.Number(meanvalue).eq(null)){ 
 
   feature = feature.set({'mean': 0})
 }
  feature = feature.setGeometry(null);
  return feature
}

 var water_district = water_district.map(removegeo); 



Export.table.toDrive({
  collection:water_district,
  description: 'Tablebydistrict',
  fileFormat: 'CSV'
});  

Answer 1

First, you need to read and understand this: https://developers.google.com/earth-engine/guides/client_server#conditionals

But it's better to not use a conditional at all here (ie: don't use ee.Algorithms.If, except as a last resort). Instead, you can get the value with a default and re-set it. (But you need to convert the feature to a dictionary first to use the get-with-default).

function removegeo(feature) {
   var meanvalue = feature.toDictionary().get('mean', 0)
   return feature.set('mean', meanvalue)
}