Loadash对多列进行分组和求和

Question

In my Vue app I need to group an array by date and then sum multiple columns. I was able to group and sum 1 column this way:

receiptsByDate: function(){
   let byDate = _.groupBy(this.receipts, 'date');
   let totals = {};
   _.forEach(byDate, function(amounts, Date){
   totals[Date] = _.reduce( byDate[Date], function(sum, receipt){
   return sum + parseFloat( receipt.total );
   }, 0);
   })
   return totals;   
}

which creates an object date: total.

This is a receipt sample on which the function is applied:

card_commission:null
created_at:"2019-11-14 06:13:20"
customer_id:null
date:"2019-11-14"
discount:"12000.0"
id:1
location_id:null
number:"2019-00001"
service:null
subtotal:"200000.0"
table_id:null
taxes:null
ticket_id:1
total:"188000.0"
updated_at:"2019-11-14 06:13:20"

I need instead to group by date but beside receipt.total I need to sum other columns like discount, subtotal and so on. I did not find anything online to achieve this. Anyone can point me in the right direction? It doesn't have to be with loadash another approach is ok too.

Answer 1

Instead of returning only total, you can return an object consist of all computed values for every date.

receiptsByDate: function(){
  let byDate = _.groupBy(this.receipts, 'date');

  let computedData = {};
  _.forEach(byDate, function(receiptList, date){
    computedData[date] = {
      total: _.sumBy(receiptList, function(receipt) {
        return parseFloat(receipt.total);
      }),
      discount: _.sumBy(receiptList, function(receipt) {
        return parseFloat(receipt.discount);
      })
    }
  };

  return computedData;
}

Answer 2

Change reduce to another forEach. If you want to use Date as key, then

let sumary = {}
_.forEach(byDate[Date], (receipt) => {
   if(sumary.total == null)
      sumary.total = parseFloat(receipt.total)
   else
      sumary.total += parseFloat(receipt.total)

   if(sumary.other== null)
      sumary.other= parseFloat(receipt.other)
   else
      sumary.other+= parseFloat(receipt.other)
}
totals[Date] = summary

If this is what you want, then you could improve your code, just replace 0 with { total: 0, other: 0} and calculate inside the reduce function.