Question

I have three textboxes, when I modify either textbox A or Textbox B Textbox C should change to A*B e.g. If A is 3 and B is 4 C is 12… if i change B to 5 C should automatically change to 15. js fiddle here: http://jsfiddle.net/Lazyboy4ever/mfyh2/

Answer 1

Bind the .change() event handler to inputs A and B, convert their value to a number using parseFloat(), multiply them, and assign the result to C:

$("[name='qty'],[name='b']").change(function () {
   var $tr = $(this).closest("tr"),
       qty = $tr.find("[name='qty']").val(),
       b = $tr.find("[name='b']").val();

   var c = parseFloat(qty) * parseFloat(b); 
   $tr.find("[name='c']").val(c);
});​

DEMO.