How to use a variable for mapReduce in MongoDB with NodeJS

Question

I have a collection of events that look like

{
  _id: BSONID
  name: "event_name",
  values: {a: 10, b: 1000, c: 50}
}

I'm trying to use mapReduce them using

map = function() {
  return emit([this.name, this.values['a']], this.values['b']);
}

reduce = function(key, values) {
  // stuff
}

collection.mapReduce(map, reduce, { out: { inline: 1 } }, callback);

However, I would like to be able to dynamically change which values I map against. In essence, I'd like to have

var key = 'a';
var value = 'b';

map = function ()
{
  return emit([this.name, this.values[key]], this.values[value]);
}

The problem is that the execution context isn't passed to mongodb. Any solution that doesn't rely on using string for functions?

kristina · Accepted Answer · 2012-05-23 15:49:38Z

2

Yes, you can pass a "scope" variable to MapReduce:

scope = {key : "a", value : "b"};
collection.mapReduce(map, reduce, {scope : scope, out: { inline: 1 } }, callback);

answered May 23, 2012 at 15:49

kristina

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1 Comment

kjetildm Over a year ago

how can you reach the context inside ::map ? -> this.context ?

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