mongo-map

When working with mongoDB Aggregation Framework sometimes you need to transform a field based on plain js map object. Consider you have:

var map = {
	forThisKey: 'retrun this value',
	thisKeyEqualsTo: 'something like this',
	andForThisOne: 'return some other string'
};

In regular js code you would do:

var value = map[key];

This module helps you do the same inside aggregation framework pipeline.

npm install mongo-map

Requirements

var getInMap = require('mongo-map');

db.myCollection.aggregate([
	{ $project: {
		value: getInMap(map, '$key')
	} }
]);

Here getInMap expands your map object into a balanced search tree that aggregation framework uses to efficiently look up your key.