Mongo Aggregation Framework helper function to perform rounding of numbers
npm install mongo-roundHelper function to perform rounding of numbers when working with mongoDB Aggregation Framework.
npm install mongo-round
``javascript`
var round = require('mongo-round');
To zero decimal places:javascript`
db.myCollection.aggregate([
{ $project: {
roundValue: round('$value')
} }
]);
To two decimal places:javascript`
db.myCollection.aggregate([
{ $project: {
roundAmount: round('$amount', 2)
} }
]);
To cents and from cents - saves from rounding errors for armithmetic operations on financial data:javascript`
db.myCollection.aggregate([
{ $project: {
amountCents: round({$multiply:['$amount', 100]})
} },
{ $group: {
_id: null, amountCents: {$sum: '$amountCents'}
} }
{ $project: {
amount: round({$divide:['$amountCents', 100]}, 2)
} }
]);
Note that for negative numbers rounding is done using absolute values, which is fitting for financial data:
`
round(-0.5) will give -1