ASPX JavaScript通过ID获取元素值

Question

I'm trying to get value from ASPX element with JavaScript but getting

Uncaught TypeError: Cannot read property 'value' of null Error .

This is HTML markup:

<tr>
    <td>Labour Cost:</td>
    <td><asp:Label ID="lbllabourCost" runat="server" /></td>
</tr>

And below is my JavaScript:

 <script>
    var labcost = document.getElementById('<%= lbllabourCost %>').value;
    console.log(labcost);
 </script>

What am I doing wrong here?

Answer 1

Consider using the ClientID property, which will resolve the client-side id attribute present for that control :

var labcost = document.getElementById('<%= lbllabourCost.ClientID %>').innerHTML;

Additionally, you may want to consider which property that you are targeting within Javascript (ie using innerHTML or textContent since you are targeting a label).

Answer 2

Probably two things.

First the ID to get the element in DOM and then to get the contents.

Try :

var labcost = document.getElementById('<%= lbllabourCost.ClientID %>').textContent;