node-mapred

Map Reduce implementation of mongodb for nodejs

Description

This lib would help you to apply mongodb mapReduce operation on array of objects

Usecases

1. For Example if you want to apply mapReduce operation on documents after aggregation pipeline then you may pass the result to this lib and perform Map Reduce operation
2. If you have a list of data that you want to combine by some department or etc criteria

Installation

npm i node-mapred --save

Usage

var MapRed = require("node-mapred");

var mapred = new MapRed();


var info = [{
    type: "fruit",
    name: "apples",
    qty: 21
}, {
    type: "fruit",
    name: "mangoes",
    qty: 23
}, {
    type: "fruit",
    name: "apples",
    qty: 2
}, {
    type: "fruit",
    name: "mangoes",
    qty: 3
}, {
    type: "animal",
    name: "dogs",
    qty: 3
}, {
    type: "animal",
    name: "cats",
    qty: 3
}, {
    type: "animal",
    name: "dogs",
    qty: 7
}]

mapred.exec(info)
    .map(function () {
        mapred.emit(this.name, this.age)
    })
    .reduce(function (key, values) {
        return values.reduce((sum, val) => sum + val);
    })
    .result(function (result) {
        console.log(result); 
        // Output [ { _id: 'apples', value: 23 }, { _id: 'mangoes', value: 26 } ]
    })


mapred.exec(info)
    .map(function () {
        var self = this
        var key = {
            type: self.type,
            name: self.name
        }
        mapred.emit(key, this.qty)
    })
    .reduce(function (key, values) {
        return values.reduce((sum, val) => sum + val);
    })
    .result(function (result) {
        console.log(result); 
        // Output
        // [ { _id: { type: 'fruit', name: 'apples' }, value: 23 },
        // { _id: { type: 'fruit', name: 'mangoes' }, value: 26 },
        // { _id: { type: 'animal', name: 'dogs' }, value: 10 },
        // { _id: { type: 'animal', name: 'cats' }, value: 3 } ]
    })

Test

npm install
npm test

License

MIT