jQuery Simple Example

HTML

<script src="//www.addressfinder.co.nz/assets/v2/widget.js"></script>
<div id="field1">

</div>
<div id="dropdownDiv" style="display:none">
    <div class="form-group">
<label>Property Investors</label>
        <div class="col-md-10">
           <select id="select1" name = select1>
              <option value="volvo">Volvo</option>
              <option value="saab">Saab</option>
              <option value="mercedes">Mercedes</option>
              <option value="audi">Audi</option>
            </select>
        </div>
    </div>
</div> 
<button type="submit" name="txtAddnew" Id="addDropdown"> Add Dropdown</button>

CSS

body {
    padding: 5px;
}

label {
    font-weight: bold;
}

input[type=text] {
    width: 20em
}

p {
    margin: 1em 0 0;
}

JavaScript

$(document).ready(function() {

  $('#addDropdown').click(function () {
    var index = (new Date()).getTime();
    var clone1 = $('#dropdownDiv').clone();        
    $(clone1).find('select').attr("id", index);      
    $(clone1).find('select').attr("name", "PropertyInvestor[" + index +"]");    
    $('#field1').append(clone1.html());
});

});