Loop through array of objects and return sum of each total values by object element id

Question

I\'m calculating taxes for a very complicate invoicing approach. I can\'t explain the whole process but if you have questions I will answer as best as I can

Answer 1

Use the reduce method:

selected_taxes.reduce(function (p, c) {
    if (p[c["tax_id"]]) {
        p[c["tax_id"]]["total_tax"] += +c["tax_value"];
    } else {
        p[c["tax_id"]] = {
            "tax_name": c["tax_name"],
            "total_tax": +c["tax_value"]
        }
    }
    return p;
}, {});

This returns a new object containing the desired data:

{
    "1": {
        "tax_name": "GST 5%",
        "total_tax": 26.46
    },
    "2": {
        "tax_name": "HST 13%",
        "total_tax": 34.39
    },
    "3": {
        "tax_name": "QST 9.975%",
        "total_tax": 52.76
    }
}

DEMO