Question

I’m trying to have a field appear in a form for when the user selects an option from a dropdown – i.e. if they select “Other” from a dropdown, a field appears below the dropdown saying “Please specify”. I can’t seem to get it to work at all – the “please specify” field appears visible all the time. Where am I going wrong? Thanks!

<script>
$(function(){
    $("#pref-select").change(function(){
        if ($("#pref-select").val()=="Other"){
            $("#other-pref").show();
        } else {
            $("#other-pref").hide();
        }
    })
})
</script>

<div class="field">
  <%= f.label :pref %><br />
  <%= f.select :pref, ["", "1", "2", "Other"], {:id => "pref-select"} %>
</div>
<div class="field" id="other-pref">
  <%= f.label :other_preference %><br />
  <%= f.text_area :other_pref %>
</div>

Answer 1

You can do it like this:
http://jsfiddle.net/vooboo13/RK97r/1/

You give the fields you don’t want to show css values of display:none;

You then use jQuery to watch for a certain value and display it if it’s that value.

HTML:

Select “fiat”, and see magic happen

<form action="" id="cars">
    <select name="cars" id="car_selector">
        <option value="volvo">Volvo</option>
        <option value="saab">Saab</option>
        <option value="fiat">Fiat</option>
        <option value="audi">Audi</option>
    </select>
    <p>&nbsp;</p>
    <label class="hidden_option">Why would you DO that?</label>
    <input type="text" name="reason" class="hidden_option" />
</form>

JS:

$(document).ready(function(){
    $("#car_selector").change(function(){
        if($("#car_selector").val() == "fiat"){
          $(".hidden_option").fadeIn('fast');   
        }            
    });        
});

CSS:

.hidden_option{
 display: none;   
}