node-mapred

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

• 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
• 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