JavaScript > onChange inputs & selects update textarea
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I have a form for editing a ticket that requires a "Reason for Edit".  What I would like to do is have that automatically filled in as a result of when any of the input fields or the select dropdown changes.  I know this can be done with javascript and an onChange event and have it modify (I believe) the innerHTML of the textarea.  I'm strong on PHP/MySQL but javascript is definitely my weakness.

What I do not know and have been unsuccessful searching for, is exactly how to code this.  As an example of what I have would be the following code:

    <!-- Customers name -->
    <input type='text' name='customer_name' onChange="updateReason('Updated Customer Name')" /><br><br>

    <!-- Customer Email -->
    <input type='text' name='customer_email' onChange="updateReason('Updated Customer Email')" />

If either of those two would be changed then the contents of a textarea would be updated and end with a carriage return.

Any help (or even pushed in the right direct / links to a guide) is appreciated.