Question

I have a table with inputs in each cell, except one (.total) which specifies the total of each table row. When one of the inputs are changed I would like the sum to change for that row. Below is far as I have been able to get.
The HTML:

<table>
   <tr>
      <td><input value = "100"/></td>
      <td><input value = "100"/></td>
      <td><input value = "100"/></td>
      <td class="total">300</td>
   </tr>
   <tr>
      <td><input value = "200"/></td>
      <td><input value = "200"/></td>
      <td><input value = "200"/></td>
      <td class="total">600</td>
   </tr>
</table>

Now for the jQuery:

    //add keyup handler
    $(document).ready(function(){
        $("input").each(function() {
            $(this).keyup(function(){
                newSum();
            });
        });
    });

    function newSum() {
        var sum = 0;
        var thisRow = $(this).closest('tr');

        //iterate through each input and add to sum
        $(thisRow).("td:not(.total) input:text").each(function() {
                sum += this.value;            
        });

        //change value of total
        $(thisRow).(".total").html(sum);
    }

Any help in finding out what I’ve done wrong will be greatly appreciated. Thanks!

Answer 1

Your main problem is the use of this in your function. If you place the body of that function directly in the keyup handler, it should work. But this in the body of a separately declared function will refer, essentially, to the object of which it is a method. And that object, in the case above, would be window.

Try this:

$(document).ready(function(){
    $("input").each(function() {
        var that = this; // fix a reference to the <input> element selected
        $(this).keyup(function(){
            newSum.call(that); // pass in a context for newsum():
                               // call() redefines what "this" means
                               // so newSum() sees 'this' as the <input> element
        });
    });
});

You also have some more superficial errors in newSum():

function newSum() {
  var sum = 0;
  var thisRow = $(this).closest('tr');

  thisRow.find('td:not(.total) input:text').each( function(){
    sum += parseFloat(this.value); // or parseInt(this.value,10) if appropriate
  });

  thisRow.find('td.total input:text').val(sum); // It is an <input>, right?
}