Show Hide Textbox using Javascript in ASP.Net

Question

This code not working in ASP.Net and give the error

Microsoft JScript runtime error: 'select' is null or not an object

my code is

var select = document.getElementsByTagName("Dd_Select_Month_Year")[0];
       select.onchange = function () {
           if (select.value == "2") {
               document.getElementsByTagName("txtDateFrom")[1].style.display = "inline";
               document.getElementsByTagName("txtDateTo")[1].style.display = "inline";
           } else {
               document.getElementsByTagName("txtDateFrom")[1].style.display = "none";
               document.getElementsByTagName("txtDateTO")[1].style.display = "none";
           }

       }

I try too much search of this platform but i cant get the solution of this issue — Raheel
– Raheel, Commented Jun 13, 2013 at 11:21
Try to replace all your 'getElementsByTagName' to 'getElementsById' in notepad or whatever. — choz
– choz, Commented Jun 13, 2013 at 11:23
It would be helpful if you post markup as well. Also watch for txtDateTo vs. txtDateTO - some browsers are case-sensitive. — Ondrej Svejdar
– Ondrej Svejdar, Commented Jun 13, 2013 at 11:30

c.P.u1 · Accepted Answer · 2013-06-13 11:29:31Z

2

Tag name is the HTML element's tag name. For a <select> element, the tag name is "select". Since there is no element with a tag "Dd_Select_Month_Year", getElementsByTagName() returns null.

Use

document.getElementsByTagName("select")[0];

Or if "Dd_Select_Month_Year" is your select's name attribute's value, that is,

<select name="Dd_Select_Month_Year">...</select>

use:

document.getElementsByName("Dd_Select_Month_Year")[0];

edited Jun 13, 2013 at 11:29

answered Jun 13, 2013 at 11:22

c.P.u1

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1 Comment

Raheel Over a year ago

Thanks C.P.u1 and also Vadz for help and slove my problem but one thing that how we write select with asp.net tags

Satpal · Accepted Answer · 2013-06-13 11:25:02Z

1

select as variable name should be avoided.

Reference:

Try to use other word as variable name

var select2 = document.getElementsByTagName("Dd_Select_Month_Year")[0];
select2.onchange = function () {
    //Do whatever
}

answered Jun 13, 2013 at 11:25

Satpal

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