How to add numbers in javascript

total_subtotals.js

updateTotalManualFeeSubTotals = function() {
  var subtotal;
  subtotal = 0.0;
  $("td.manual-fee-sub-total").map(function() {
    var value;
    value = parseFloat(this.innerHTML.replace("$", ""));
    if (!isNaN(value)) {
      return value;
    }
  }).each(function(i, e) {
    return subtotal += parseFloat(e) || 0.0;
  });
  return subtotal;
};