Build “value” for text area base on input and checkbox

Question

As the question said, how can I build a context for a textarea , say I don't want or I can't modified the controller or the models of a Framework, but I can change the or add fields to the "views/templates", so say this is my template:

<form>
    <input name="name" id="name">
    <input name="lastname" id="lastname">
    <textarea name="onservations" id="observations"></textarea>
</form>

Say thats all there is for the form, but I need to add a few other inputs but the extra input are not defined on the controller or model and they also need to be save and I only know a bit of HTML so please bear with me on this one...

So since I can not add or modifid the controller or model, I can only assume that I can add my extra field to the template and then pass them along to the textarea in basic html since the framewok wont strip the basic html tags, I can use p , em , a , b , strong , i , table , img ... so my new form will be like this:

<form>
    <input name="name" id="name">
    <input name="lastname" id="lastname">
    <div id="original_text" style="display: none;">
        <textarea name="observations" id="observations"></textarea>
    </div>

    <!-- Extra Field -->
    <input type="text" name="what">
    <input type="radio" value="Yes" id="yes_r" name="n_rs">Yes
    <input type="radio" value="No" id="no_r" name="n_rs" >No
    <textarea name="observations_2" id="observations_2"></textarea>
</form>

So there are my extra field, now, how can I pass the values of the extra fields to the textarea with the ID "observations" say the user checks Yes and in "What" he/she type something, and then on the "observations_2" type something else...
so the value for the original textarea would be something like this:

<p>What happen?: [value from input text name what]</p>
<p>Would you like a candy? [value from the radio buttons named n_rs]</p>
<p>Your observations are: [value from textarea named observations]</p>

And those 3

get saved on the data base under the column "observations", now, remember, the controllers or models or helpers can not be modified I can not add other columns to the data base so I have to work with what I have, and my only solution is to do a jquery that can pass those values to that textarea...
So how is the jquery would look like?
Thank for taking the time.

Answer 1

This should concatenate your values, then put the formatted string into your textarea . It will "refresh" your textarea if any of the elements change:

$('#observations_2, input[name=what], input:radio[name=n_rs]').on("keyup change", function(){
    var allTogether = 
        "What happen?: " + 
        $('input[name=what]').val() +
        "\n" +
        "Would you like a candy? " +
        $('input:radio[name=n_rs]:checked').val() +
        "\n" +
        "Your observations are: " +
        $('#observations_2').val()
    ;
    $('#observations').val(""); // First clear it
    $('#observations').val(allTogether); // Then rebuild it
});

Fiddle: http://jsfiddle.net/QWau9/