How do I set the value of an input field via javascript

Question

Can someone tell me why this markup/script errors out and doesnt put "Waltdog" into the Hidden1 input field?

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<script>
    document.getElementById("Hidden1").value = 'Waltdog';
</script>
<body>
    <form id="form1" runat="server">
        <div>
            <input id="Hidden1" type="hidden" runat="server" /> 
            Let me know if you see this!!! You crazy Texicans are harshing my Wednesday vibe! :)
        </div>
    </form>
</body>

Jamiec · Accepted Answer · 2012-05-16 15:59:54Z

3

Because your script runs before the element exists.

HTML (along with javascript in script tags) in is interpreted top to bottom, therefore when the script runs, the input element has not yet been created.

The solution is either

put the script in a function that runs when the page loads
put the javascript after the element

answered May 16, 2012 at 15:59

Jamiec

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2 Comments

hielsnoppe Over a year ago

That's right and here is an example of how to achieve the first one: Wrap your code in a function e.g myfunction() and in the HTML write <body onload="myfunction();"> ....

Talon Blackthorne Over a year ago

<html xmlns="w3.org/1999/xhtml"> <head runat="server"> <title></title> </head> <script> function LoadFunc() { document.getElementById("Hidden1").value = 'Waltdog'; } </script> <body> <form id="form1" runat="server"> <div> <input id="Hidden1" type="hidden" runat="server" /> Let me know if you see this!!! You crazy Texicans are harshing my Wednesday vibe! :) </div> </form> <script>LoadFunc()</script> </body> </html>

Artem Latyshev · Accepted Answer · 2012-05-16 17:01:17Z

0

Put script node below input

<input id="Hidden1" type="hidden" runat="server" /> 
<script>
    document.getElementById("Hidden1").value = 'Waltdog';
</script>

answered May 16, 2012 at 17:01

Artem Latyshev

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