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

I think Array.prototype.reduce will be your best bet for this:

var totals = data.reduce(function(c,x){
    if(!c[x.tax_id]) c[x.tax_id] = {
        tax_name: x.tax_name,
        tax_id: x.tax_id, 
        total_tax: 0
    };
    c[x.tax_id].total_tax += Number(x.tax_value);
    return c;
}, {});

This approach generates an object that has, as its properties, the tax ID numbers. If you really want a flat array from that, you can convert that into an array after the fact:

var totalsArray = [];
for(var taxId in totals){
    totalsArray.push(totals[taxId]):
}

Demonstration: http://jsfiddle.net/3jaJC/1/