js获取listbox的值

<select id="myListBox">
  <option value="option1">Option 1</option>
  <option value="option2">Option 2</option>
  <option value="option3">Option 3</option>
</select>

<script>
  function getSelectedValue() {
    var listBox = document.getElementById("myListBox");
    var selectedValue = listBox.options[listBox.selectedIndex].value;
    console.log(selectedValue);
  }
</script>

<select id="myListBox" multiple>
  <option value="option1">Option 1</option>
  <option value="option2">Option 2</option>
  <option value="option3">Option 3</option>
</select>

<script>
  function getSelectedValues() {
    var listBox = document.getElementById("myListBox");
    var selectedValues = [];
    for (var i = 0; i < listBox.options.length; i++) {
      if (listBox.options[i].selected) {
        selectedValues.push(listBox.options[i].value);
      }
    }
    console.log(selectedValues);
  }
</script>

window.onload = function() {
  // 你的代码
};