按日期分组数据（年）Vue.js

Question

I am trying to group my datas by date: dates with the same year belong to a group. i want to group invoices by data_emissione,which have the following structure:

        invoices: [
         {id,data_emissione:"2017-06-19 00:00:00"},
         {id,data_emissione:"2017-05-19 00:00:00"},
         {id,data_emissione:"2018-06-24 00:00:00"}
        ]

, but the following method returns nothing.

export default {
        data(){
            return {
                invoices:[],
                groups:{}

            }
        },
 mounted(){
            this.getMine();
            this.groupInvoices();
        },
 methods:{
            groupInvoices(){
                var self = this;
                var groups = _.groupBy(self.invoices,function(d){
                    return moment(d.data_emissione).year().format();
                });

            },

Any kind of help would be appreciated

Answer 1

Remove .format() and it should work:

export default {
    data(){
        return {
            invoices:[
                {data_emissione:"2017-06-19 00:00:00"},
                {data_emissione:"2017-05-19 00:00:00"},
                {data_emissione:"2018-06-24 00:00:00"}
            ],
            groups: {}
        }
    },
    mounted(){
        this.getMine();
        this.groupInvoices();
    },
    methods:{
        groupInvoices(){
            var self = this;
            var this.groups = _.groupBy(self.invoices,function(d){
                return moment(d.data_emissione).year();
            });

        },
    }
}

Answer 2

This is what I do most of the times:

1. retrieve raw data
2. format them adding props
3. manipulate formatted data

You can also use lodash groupBy but most of the times I want an array or arrays and not an object of arrays.

 // retrieve let invoices = [ {id: 1, data_emissione: "2017-06-19 00:00:00"}, {id: 2, data_emissione: "2017-05-19 00:00:00"}, {id: 3, data_emissione: "2018-06-24 00:00:00"}] // format let formattedInvoices = invoices.map(elem => ({ id: elem.id, data_emissione: elem.data_emissione, year: moment(elem.data_emissione).year() })); // manipulate let groupedInvoices = [2017, 2018].map(year => formattedInvoices.filter(elem => elem.year === year)) console.log(groupedInvoices) 

 <script src="https://momentjs.com/downloads/moment.min.js"></script> 

Answer 3

An attempt to make previous answer better:

// retrieve
const invoices = [
    {id: 1, data_emissione: "2017-06-19 00:00:00"},
    {id: 2, data_emissione: "2017-05-19 00:00:00"},
    {id: 3, data_emissione: "2018-06-24 00:00:00"}]

  const groupedInvoices = {};

  invoices.forEach((invoice) => {
    const year = moment(invoice.data_emissione).year();
    groupedInvoices[year] = groupedInvoices[year] || [];
    groupedInvoices[year].push(invoice);
  });

Just use object with keys - years and avoid using another data array.