Javascript -如何将选择值记录为多选下拉列表中的数组(包括添加和删除)

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

var selectedValues = [];

selectElement.addEventListener("change", function() {
  selectedValues = Array.from(selectElement.selectedOptions).map(option => option.value);
});

selectedValues.push(newValue);

var index = selectedValues.indexOf(valueToRemove);
if (index > -1) {
  selectedValues.splice(index, 1);
}

var selectElement = document.getElementById("mySelect");
var selectedValues = [];

selectElement.addEventListener("change", function() {
  selectedValues = Array.from(selectElement.selectedOptions).map(option => option.value);
});

function addValue(newValue) {
  selectedValues.push(newValue);
}

function removeValue(valueToRemove) {
  var index = selectedValues.indexOf(valueToRemove);
  if (index > -1) {
    selectedValues.splice(index, 1);
  }
}