Would not it be better to create an object with the keys each month? Something like this:
let json = [{"valor":"100","dt_month":"11"},
{"valor":"150","dt_month":"11"},
{"valor":"1324.50","dt_month":"9"},
{"valor":"12.35","dt_month":"5"}]
let result = {};
for(var i of json){
if(!(i["dt_month"] in result)){
result[i["dt_month"]] = 0;
}
result[i["dt_month"]] += parseFloat(i["valor"]);
}
In this case, to access the values just put result["<valor_do_mês>"]
.
If you really want to do with two vectors, it should look like this:
let json = [{"valor":"100","dt_month":"11"},
{"valor":"150","dt_month":"11"},
{"valor":"1324.50","dt_month":"9"},
{"valor":"12.35","dt_month":"5"}]
let dates = [];
let sums = [];
for(var i of json){
if(dates.indexOf(i["dt_month"]) < 0){
dates.push(i["dt_month"]);
sums.push(0);
}
sums[dates.indexOf(i["dt_month"])] += parseFloat(i["valor"]);
}