[html] form, select

HTML

<select>
    <option value="">--select--</option>
    <option value="red">red</option>
    <option value="green">green</option>
    <option value="blue">blue</option>
</select>

<button class="btn2">reset selected</button>
<button class="btn3">selected values</button>

<div class="output"></div>

CSS

.output {
    border: 1px solid lightgray;
    height: 20px;
}

JavaScript

document.addEventListener('DOMContentLoaded', function(e) {
    var btn2 = document.querySelectorAll('.btn2')[0];
    var btn3 = document.querySelectorAll('.btn3')[0];
    btn2.addEventListener('click', function(e) {
        document.querySelectorAll('select')[0].selectedIndex = -1;
    });
    btn3.addEventListener('click', function(e) {
        document.querySelectorAll('.output')[0].innerHTML = document.querySelectorAll('select')[0].value;
    });
});