console.clear();

var db = new PouchDB('friendsdb');

//db.destroy();

​

var docs = [{

  '_id': '1',

  'number': 10,

  'values': '1, 2, 3',

  'loto': 'fooloto'

}, {

  '_id': '2',

  'number': 12,

  'values': '4, 7, 9',

  'loto': 'barloto'

}, {

  '_id': '3',

  'number': 13,

  'values': '9, 4, 5',

  'loto': 'fooloto'

}];

​

db.bulkDocs(docs).then(function(result) {

  querySum();

  queryLargest();

  querySmallest();

  queryAverage();

}).catch(function(err) {

  console.log(err);

});

​

function querySum() {

  function map(doc) {

    // the function emit(key, value) takes two arguments

    // the key (first) arguments will be sent as an array to the reduce() function as KEYS

    // the value (second) arguments will be sent as an array to the reduce() function as VALUES

    emit(doc._id, doc.number);

  }

  function reduce(keys, values, rereduce) {

    // keys:

    //   here the keys arg will be an array containing everything that was emitted as key in the map function...

    //   ...plus the ID of each doc (that is included automatically by PouchDB/CouchDB).

    //   So each element of the keys array will be an array of [keySentToTheEmitFunction, _idOfTheDoc]

    //

    // values

    //   will be an array of the values emitted as value

    console.info('keys ', JSON.stringify(keys));

    console.info('values ', JSON.stringify(values));

    // check for more info: http://couchdb.readthedocs.io/en/latest/couchapp/views/intro.html

    // So, since we want the sum, we can just sum all items of the values array

    // (there are several ways to sum an array, I'm just using vanilla for to keep it simple)

    var i = 0, totalSum = 0;

    for(; i < values.length; i++){

        totalSum += values[i];

    }

    return totalSum;

  }

  db.query({map: map, reduce: reduce}, function(err, response) {

    console.log('sum is ' + response.rows[0].value);

  });

}

​

function queryLargest() {

  function map(doc) {

    emit(doc._id, doc.number);

  }

  function reduce(keys, values, rereduce) {

    // everything same as before (see querySum() above)

    // so, this time we want the larger element of the values array

    // http://stackoverflow.com/a/1379560/1850609

    return Math.max.apply(Math, values);

  }

  db.query({map: map, reduce: reduce}, function(err, response) {

    console.log('largest is ' + response.rows[0].value);

  });

}

​

function querySmallest() {

  function map(doc) {

    emit(doc._id, doc.number);

  }

  function reduce(keys, values, rereduce) {

    // all the same... now the looking for the min

    return Math.min.apply(Math, values);

  }

  db.query({map: map, reduce: reduce}, function(err, response) {

    console.log('smallest is ' + response.rows[0].value);

  });

}

​

function queryAverage() {

  function map(doc) {

    emit(doc._id, doc.number);

  }

  function reduce(keys, values, rereduce) {

    // now simply calculating the average

    var i = 0, totalSum = 0;

    for(; i < values.length; i++){

        totalSum += values[i];

    }

    return totalSum/values.length;

  }

  db.query({map: map, reduce: reduce}, function(err, response) {

    console.log('average is ' + response.rows[0].value);

  });

}