Modify java script in GTM to include product subtotal

Question

I've trying to figure this one out since my dev is not able to pass subtotal value by product. Any help is greatly appreciated.

I added this script in GTM java script variable in order to create a product array based on data layer. But I need to add product subtotal , which should pass value of productPrice * productQuantity .

function()
{

var productName = {{dlv - productName}};
var productId = {{dlv - productId}};
var productPrice = {{dlv - productPrice}};
var productBrand = {{dlv - productBrand}};
var productCategory = {{dlv - productCategory}};
var productVariant = {{dlv - productVariantTitle}};
var productQty = {{dlv - productQuantity}};
var productSku = {{dlv - productSku}};
var productSubtotal = ;
var items = [];

for( i = 0; i < productId.length; i++ ){
    items.push(     
        {
          'item_name': productName[i],
          'item_id': productId[i],
          'item_brand': productBrand[i],
          'item_category': productCategory[i],
          'item_variant': productVariant[i],
          'price': productPrice[i],
          'quantity': productQty[i],
          'sku': productSku[i],  
          'subtotal': productSubtotal[i],
        }
    );
}
return items;
}

I tried few options but either get total product value (all products summed up instead of itemised), or no value at all.

In this case, i tried adding a new GTM variable to pass the total amount, but i need totals by product.

function(){
  var productList={{DL - Checkout - Products}};
  var totalAmount=0;
  for(var i=0;i<productList.length;i++)
  {
    totalAmount+=(productList[i].quantity)*(parseFloat(productList[i].price));
  }
  return totalAmount;
}

Answer 1

I think you already know the concept. But didn't put it together

function(){
    var productName = {{dlv - productName}};
    var productId = {{dlv - productId}};
    var productPrice = {{dlv - productPrice}};
    var productBrand = {{dlv - productBrand}};
    var productCategory = {{dlv - productCategory}};
    var productVariant = {{dlv - productVariantTitle}};
    var productQty = {{dlv - productQuantity}};
    var productSku = {{dlv - productSku}};
    var productSubtotal = 0;
    var items = [];

    for( i = 0; i < productId.length; i++ ){
        productSubtotal = productQty[i] * parseFloat(productPrice[i]);
        items.push({
              'item_name': productName[i],
              'item_id': productId[i],
              'item_brand': productBrand[i],
              'item_category': productCategory[i],
              'item_variant': productVariant[i],
              'price': productPrice[i],
              'quantity': productQty[i],
              'sku': productSku[i],  
              'subtotal': productSubtotal,
        });
    }
    return items;
}

Just make the subtotal in the for loop and before the items.push