Dependent Dropdown about choices

[jshjohnson]

This is technically already possible. I've made an example below for you:

<label for="cities">States</label>
<select name="cities" id="cities" placeholder="Choose a state">
    <option value="Texas">Texas</option>
    <option value="Chicago">Chicago</option>
    <option value="New York">New York</option>
    <option value="Washington">Washington</option>
    <option value="Michigan">Michigan</option>
</select>

<label for="boroughs">Boroughs</label>
<select name="boroughs" id="boroughs" placeholder="Choose a borough">
    <option value="The Bronx">The Bronx</option>
    <option value="Brooklyn">Brooklyn</option>
    <option value="Manhatten">Manhatten</option>
    <option value="Queens">Queens</option>
    <option value="Staten Island">Staten Island</option>
</select>

document.addEventListener('DOMContentLoaded', function() {
    var cities = new Choices(document.getElementById('cities'), {
        callbackOnChange: function(value) {
            if(value === 'New York') {
                boroughs.enable();
            } else {
                boroughs.disable();
            }
        }
    });

    var boroughs = new Choices(document.getElementById('boroughs')).disable();
});

You could of course do some fancier validation on the value but you get the idea!

Thanks