D3.js: get value of selected option?

D3.js: get value of selected option?

I want to get the value of the selected option from a dropdown list, in
D3.js.
<select>
<option data-graph="1">1</option>
<option value="2">2</option>
</select>
I have seen this question which explains how to get the value when the
select changes:
d3.select("#myselect").on("change", change)
function change() {
this.options[this.selectedIndex].value
}
But how can I get the selected value on page load, not when the select is
changed?