Data validation for donuts

The JavaScript we wrote in the previous post is really basic. Let's improve it a bit adding some data validation.

We rewrite the placeOrder() function, to check any required field. So, name should not be empty, pickup should be a number, and the sum of the requested donuts should be greater than zero.

If we detect some non numeric data in a field that is expected to be numeric, we reset it to empty string:

function placeOrder(form) {

  if(document.getElementById("name").value == "") {
    alert("Your name is mandatory!");
    return;
  }

  var pickup = document.getElementById("pickup");
  if(pickup.value == "" || isNaN(pickup.value)) {
    alert("Please, specify the pickup time");
    pickup.value = "";
    return;
  }

  var cDonuts = parseInt(document.getElementById("cdonuts").value);
  if(isNaN(cDonuts)) {
    cDonuts = 0;
    document.getElementById("cdonuts").value = "";
  }
  var gDonuts = parseInt(document.getElementById("gdonuts").value);
  if(isNaN(gDonuts)) {
    gDonuts = 0;
    document.getElementById("gdonuts").value = "";
  }
  if(cDonuts + gDonuts == 0) {
    alert("Please, order at least one donut!");
    return;         
  }

  // Submit the order to the server
  alert("Not implemented yet!");
  //form.submit();
}

Post written while reading chapter two of Head First JavaScript, a good book if you know nothing about JavaScript and not much about programming. A bit too slow otherwise.