如何通过JavaScript获取<select>中当前选择的<option>？

var selectElement = document.getElementById("mySelect");
var selectedIndex = selectElement.selectedIndex;

var selectElement = document.getElementById("mySelect");
var selectedValue = selectElement.value;

var selectElement = document.getElementById("mySelect");
var selectedOption;
for (var i = 0; i < selectElement.options.length; i++) {
  if (selectElement.options[i].selected) {
    selectedOption = selectElement.options[i];
    break;
  }
}
var selectedValue = selectedOption.value;