从选择字段Javascript获取默认值 [英] Get Default Value From select field Javascript

问题描述

我有一个具有当前选项的选择字段，我有一个php脚本检查mysql数据库，并将select标签添加到当前使用的标签中.

I have a select field that have have present options and I have a php script check a mysql database and add a select tag to the one currently being used.

在提交之前，我需要找到一种方法来了解用户是否更改了选择字段.

I need to find a way to know if the user have changed the select field or not before submitting it.

var Access = document.forms[UIDF]["Access"].value;
var DAccess = document.forms[UIDF]["Access"].defaultIndex; <--- This is my problem. I just need to know how to get the selected option value as this keep changing with every user

<select name="Access">
  <option value="0" selected='selected'>Employee</option>
  <option value="1">Team Leader</option>
  <option value="2">Admin</option>
</select>

推荐答案

Option标记具有javascript属性defaultSelected，如果该选项在页面加载时具有selected值，则该属性会设置为true.请注意，这是option标记，而不是select标记，因此您必须遍历选项并检查属性.

The Option tag has a javascript attribute defaultSelected that's set to true if the option had a selected value on page load. Note that this is the option tag and not the select one, so you'll have to loop through the options and check for the attribute.

类似

var DAccess;
var AccessSelect = document.forms[UIDF]["Access"];

for (var i = 0 ; i<AccessSelect.length ; i++)
{
    if (AccessSelect[i].defaultSelected)
        DAccess = AccessSelect[i].value;
}

或更重要的是:

var AccessHasChanged = false;
var AccessSelect = document.forms[UIDF]["Access"];

for (var i = 0 ; i<AccessSelect.length ; i++)
{
    if (AccessSelect[i].defaultSelected && 
        AccessSelect.value != AccessSelect[i].value)
        AccessHasChanged = true;
}

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