使用JavaScript计算总计

Question

I made a from in HTML using some input fields where the user can type a number and the price will automatically update according to the number being put in:

<td>Pizza Margherita</td>
<td><input type="number" id="countMargherita" class="orderform" name="PizzaMargherita" onkeyup="validateForm(this)" min="1"></td>
<td><span id="totalMargherita"></span></td>

And the piece of JS code

var priceMagarita = 7;
    var numPizzaMargheritaInput = document.getElementById('countMargherita');
    var priceMargheritaLabel    = document.getElementById('totalMargherita');

    function onNumPizzaMargheritaInputChange(e){

        var totalMargherita = priceMargherita * parseInt(e.target.value);
        var formattedPrice = '\u20ac '+totalMargherita.toFixed(2);

        priceMMargheritaLabel.innerHTML = '';
        priceMargheritaLabel.appendChild(document.createTextNode(formattedPrice));
    }
    numPizzaMargheritaInput.addEventListener('change', onNumPizzaMargheritaInputChange, false);

Now i have 11 fields like those those are all working just fine but now i'd like to make a Total price. So one that counts all those prices together and puts them in

<td><h3>Totale Prijs</h3></td>
<td></td>
<td><span id="TotalPrice"></span></td>

But since im not experienced at all in JS i have alot of trouble accomplishing this.

Any help is greatly appeciated.

Answer 1

You can use getElementsByClassName() instead of getElementById() and deal with each element.

Maybe the following does not fit exactly what you need but you will probably adapt it easily

// create a price object with all pizzas prices
var prices = {
  PizzaMargherita : 7,
  PizzaHawai : 42
}
// get all inputs which contains number of pizzas. 
// Maybe you will add something else than "order form"
function recalculate()
{
  var all_inputs = document.getElementsByClassName('orderform');
  var total = 0;
  for(i=0;i<all_inputs.length;i++)
  {
    var that_input = all_inputs[i]
    var subtotal = parseInt(that_input.value * prices[that_input.name]);
    total += subtotal
    document.getElementById('totalMargherita').innerHTML = subtotal;
  }
  document.getElementById('totalPrice').innerHTML = total;
}
// add your listener in each inputs
var all_inputs = document.getElementsByClassName('orderform');
for(i=0;i<all_inputs.length;i++)
  all_inputs[i].addEventListener('change',function(e){recalculate(); }, false);