How to use Javascript to get ASP.NEt Web Forms label's value?

问题

I have the following label control:

<asp:Label ForeColor="DarkGreen" runat="server" ID="lblStatus"></asp:Label>

Its value is filled in the Page_Load event.

I attached the following Javascript (placed at the end of the page, not Master page):

function Validate() {
        var lblObj = document.getElementById('<%=lblStatus.ClientID%>');
        alert(lblObj.value);
        if (lblObj.value == "Replaced" || lblObj.value == 'Trashed' || lblObj.value == "Internal Use") {

            alert("Products with" + lblObj.value + "status cannot be reserved");
            return false;
        }
    }

The alert(lblObj.value) displays a popup with text "undefined". How can I fix this problem? Please, I tried many combinations for placing the JavaScript but no luck! Thanks

UPDATE

Browser soruce code:

<span id="ctl00__main_lblStatus" style="color:DarkGreen;">Available</span></td>

First line of Validate JS function:

function Validate() {
        var lblObj = document.getElementById('ctl00__main_lblStatus');

回答1:

Use JQuery and it will run in all browsers and platforms, something like:

$('#<%= lblStatus.ClientID %>').next().text();

source: JQuery: getting the value/text/innerHtml of a checkbox in an ASP.NET CheckBoxList control

回答2:

labels don't have a value. They have innerHTML and innerText.

回答3:

Label server control renders as span. So you should get it's content by innerText. try this :

alert(lblObj.innerText);

回答4:

ASP.NET label server control will be rendered in complex HTML output. Like:

<span id="ctl00_ctl00_ContentPlaceHolder1_BodyPlaceHolder_lblLanguage0">
 <label class="inputText">English</label>
</span>

When you use getElementById you will get span. But to set value via javascript you have to access inner label object

回答5:

try this

<script language="javascript" type="text/javascript">
function getlabelvalue()
{
   var value1 = document.getElementById('<%=labelID.ClientID%>').value;
            if (value1.length < 1)
                value1 = 0;
}    
 </script>

回答6:

With jquery you need to use the html method.

var g = $('#<%=lblStatus.ClientID%>').html();

These will NOT work with jquery:

$('#<%=lblStatus.ClientID%>').innerText
$('#<%=lblStatus.ClientID%>').innerHTML
$('#<%=lblStatus.ClientID%>').val()

来源：https://stackoverflow.com/questions/7431464/how-to-use-javascript-to-get-asp-net-web-forms-labels-value

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javascript

ASP.NET

label