如何使用D3.js从下拉列表中设置最后一个选项

Question

I have a drop-down list with dates as options in it:

<select id="dateSelector">
  <option value="2016-01-01">Январь 2016</option>
  <option value="2016-02-01">Февраль 2016</option>
  <option value="2016-03-01">Март 2016</option>
</select>

I need to set the last date from the list (the most recent) as selected one. I've managed to do this by specifying the date manually. So how can I do it automatically in case if more dates will appear in the list as options in the future?

d3.select("select#dateSelector")
  .selectAll("option")
  .data(uniqueDates)
  .enter()
  .append("option")
  .text(function(d) {
    return formatRU(new Date(d));
  })
  .attr("value", function(d) {
    return d;
  })
  .property("selected", function(d) {
    return d === "2016-03-01";
  });

Answer 1

You could do it based on the index of the datum instead. Let N = uniqueDates.length , then use:

.property("selected", function(d, i) { return i == N-1; })