================
on_field_changed
================

on_field_changed(field, lookup_item)

**domain**: client 

**language**: javascript

**class** :doc:`Item class </refs/client/item_api>`

Description
===========

Write an ``on_field_changed`` event handler to respond to any changes in the 
field’s data.

The ``field`` parameter is the field whose data has been changed. To get the 
item that owns the field, use the 
:doc:`owner </refs/client/field/at_owner>` 
attribute of the field.

The ``lookup_item`` parameter is not ``undefined`` when 
the field is a 
:doc:`lookup field </programming/data/lookup_fields>` 
and a change has occured 
when a user selected a record from a lookup item dataset.

Example
=======

.. code-block:: js

    function on_field_changed(field, lookup_item) {
        var item = field.owner;
        if (field.field_name === 'quantity' || field.field_name === 'unitprice') {
            item.owner.calc_total(item);
        }
        else if (field.field_name === 'track' && lookup_item) {
            item.quantity.value = 1;
            item.unitprice.value = lookup_item.unitprice.value;
        }
    }


See also
========

:doc:`Fields </programming/data/fields>`

:doc:`value </refs/client/field/at_value>`

:doc:`on_before_field_changed <on_before_field_changed>`