无法获取文本框的值并将我放入JavaScript中的变量

Question

I set the value of the textbox in Page-load and assign it into a variable in the java script. but this line wont execute.

        y = document.getElementByID("<%= TextBox1.ClientID %>").value;

it wont work either when I set value of textbox in the aspx page.

    protected void Page_Load(object sender, EventArgs e) {
 TextBox1.Text = "14";
 } 

and

 <asp:TextBox ID="TextBox1" runat="server" Text="14"></asp:TextBox>

neither of them worked -------- here is the script -----

     <script type="text/javascript">
                                var map;
                                var y;
                    y = document.getElementByID("<%= TextBox1.ClientID %>").value;
                    y = parseInt(y);

                require(["esri/map", "dojo/domReady!"], function (Map) {

                    esriConfig.defaults.map.panDuration = 1;   

                        var map = new Map("map", {
                        center: [-118, y],
                        zoom: 15,
                        basemap: "satellite"

                    });
                });
            </script>

what am i doing wrong? Everything works OK when I just assign y to a number , Is this even a good practice to get values from asp controls?

Answer 1

"<%= TextBox1.ClientID %>"

This is not getting evaluated like you think, it will just send this as a literal string to the client. Instead you should do:

y = document.getElementByID("'" + <%= TextBox1.ClientID %> "'").value;

Even so, this is quite ugly code. Since the textbox does not seem to be a dynamically generated contol, you should set it's ClientIDMode property to Static or Predictable . Then hard-code the ID in your javascript.