如果你用javascript添加这个选项

function AddNewOption(userRoutes, text, id) 
{
    var option = document.createElement("option");
    option.text = text;
    option.value = id;
    option.selected = "selected";
    userdRoutes.add(option);
}

改变

document.getElementById('personlist').getElementsByTagName('option')[11].selected = 'selected'

to

document.getElementById('personlist').value=Person_ID;

我相信博客文章JavaScript初学者-按值选择下拉选项可能会对你有帮助。

<a href="javascript:void(0);" onclick="selectItemByValue(document.getElementById('personlist'),11)">change</a>

function selectItemByValue(elmnt, value){

  for(var i=0; i < elmnt.options.length; i++)
  {
    if(elmnt.options[i].value === value) {
      elmnt.selectedIndex = i;
      break;
    }
  }
}

这是一个老帖子，但如果有人还在寻找这种问题的解决方案，以下是我想出的:

<script>
  document.addEventListener("DOMContentLoaded", function(e) {
    document.forms['AddAndEdit'].elements['list'].value = 11;
  });
</script>

工具作为处理选择框的纯JavaScript代码:

图形的理解:

图片- A

图片- B

图片- C

|小提琴手演示

JavaScript代码:

/**
 * Empty Select Box
 * @param eid Element ID
 * @param value text
 * @param text text
 * @author Neeraj.Singh
 */
function emptySelectBoxById(eid, value, text) {
    document.getElementById(eid).innerHTML = "<option value='" + value + "'>" + text + "</option>";
}


/**
 * Reset Select Box
 * @param eid Element ID
 */

function resetSelectBoxById(eid) {
    document.getElementById(eid).options[0].selected = 'selected';
}


/**
 * Set Select Box Selection By Index
 * @param eid Element ID
 * @param eindx Element Index
 */

function setSelectBoxByIndex(eid, eindx) {
    document.getElementById(eid).getElementsByTagName('option')[eindx].selected = 'selected';
    //or
    document.getElementById(eid).options[eindx].selected = 'selected';
}


/**
 * Set Select Box Selection By Value
 * @param eid Element ID
 * @param eval Element Index
 */
function setSelectBoxByValue(eid, eval) {
    document.getElementById(eid).value = eval;
}


/**
 * Set Select Box Selection By Text
 * @param eid Element ID
 * @param eval Element Index
 */
function setSelectBoxByText(eid, etxt) {
    var eid = document.getElementById(eid);
    for (var i = 0; i < eid.options.length; ++i) {
        if (eid.options[i].text === etxt)
            eid.options[i].selected = true;
    }
}


/**
 * Get Select Box Text By ID
 * @param eid Element ID
 * @return string
 */

function getSelectBoxText(eid) {
    return document.getElementById(eid).options[document.getElementById(eid).selectedIndex].text;
}


/**
 * Get Select Box Value By ID
 * @param eid Element ID
 * @return string
 */

function getSelectBoxValue(id) {
    return document.getElementById(id).options[document.getElementById(id).selectedIndex].value;
}

你也可以使用JQuery

$(document).ready(function () {
  $('#personlist').val("10");
}