javascript - 如何将文本框值添加到列表中？

Question

<分区>

Answer 1

<select id='pre-selected-options1' multiple='multiple'>
    <option value='elem_1' selected>1</option>
    <option value='elem_2'>2</option>
    <option value='elem_3'>nextoption</option>
    <option value='elem_4' selected>option 1</option>
    <option value='elem_100'>option 2</option>
    </select>
    <!-- This is the list (above)-->
    <br>
    <label>Enter: </label>
    <input type="text" name="" id="inp" class="input-default"> 
    <button type="button" onclick="add()" class="btn btn-success btn-sm m-b-10 m-l-5">Add</button>
    <!-- This is the textbox-->
    <script>
    function add()
    {
    var x = document.getElementById("pre-selected-options1");
    var option = document.createElement("option");
    option.text = document.getElementById("inp").value;
    x.add(option);
    }
    </script>