未捕获的ReferenceError：未定义getPrice_6

Question

我正在使用this guide以价格形式添加计算，将其乘以数量（按下拉列表设置）并输出为总数。

我的最终代码是：

function totalQuantity(){
  getPrice_6();
  //calculate a grand total based on the available product field
  quantity = parseInt(document.getElementById('quantity').value);
  //retrieve the value selected in the "quantity" field
  currentTotal = parseFloat(document.getElementById('total').value);
  //adjust displayed total
  total = quantity * currentTotal;
  //re-calculate the total based on the value selected in the "quantity" field
  document.getElementById('total').value = total.toFixed(2);
  //convert the "total" field's value to a float number followed by 2 decimals
  document.getElementById('payment_total_6').innerHTML = total.toFixed(2) + ' AUD';
  //display the total field's value along with the "USD" currency code
  document.getElementsByName('form[rsfp_Total]')[0].value = total.toFixed(2);
 
return true;
}
 
    window.addEvent('domready', function() {
 
totalQuantity();
    });

但是在更改数量字段时，我收到一个控制台错误：未捕获的ReferenceError：未定义getPrice_6。

根据指南，'6'是我正在使用的表单的ID。

似乎我错过了一些明显的东西，但我无法弄清楚是什么。