Can you use conditional logic within your map function to initialize a value?

I'm using a mapreduce to do a report and I ran into a "doc has no properties" and I think it is because some of the document do not have the property that I am doing calculation on.

the following is my map function:

var map = function(){
  emit(this.SurveyId, {count: 1, totalScore: : this.totalScore, networth: this.networth});}

reduce function:

var reduce = function(key,values){
  var doc = {count: 0, totalScore: 0, networth: 0};
  values.forEach(function(item){
    doc.count+=1;
    doc.totalScore+=item.totalScore;
    doc.networth+=item.networth;});
  return doc;}

finalize function:

var finalize = function(key,reduced){
  reduced.avg = reduced.totalScore/reduced.count;
  reduced.netAvg = reduced.networth/reduced.count;
  return reduced;}

map reduce call

db.SurveyResult.mapReduce(map,reduce,{finalize: finalize, out: 'my_result'})

networth is not in all document in SurveyReu开发者_开发技巧slt collection. I think this is why it failed. How do i specify so that if networth doesn't exist, use 0 instead? Thank you.

It's javascript...

if "networth" in item:
    doc.networth+=item.networth;