Can't access hidden inputbox value from javascript

Question

I want to extract a value from my hidden inputbox, by using javascript, but sometimes i am getting a "undefined" error and sometimes no output. when i did

alert(document.getElementById('hhh').value);

from inside a printIt() function i get the output. but i think somehow it is not going in to "var a", and also

var a =22;

works if i remove the

var a =document.getElementById('hhh').value;

in below code.

<script type="text/javascript">
var a =document.getElementById('hhh').value;
function startTime()
{

document.getElementById('txt').innerHTML=a;
a=a-1;
t=setTimeout('startTime()',600);
}
</script>

<body    onLoad="startTime()">
<form name="form1"   id="form11" method="post" action="">
<input type="hidden" id="hhh" name="time" value="11" />
</form>
<div id="txt"></div>
</body>

Any help would be appreciated. Thanks.

Don't pass strings to setTimeout, pass functions instead. And don't use setTimeout for something you want to keep happening, use setInterval instead. setInterval(startTime, 600); — Quentin
– Quentin, Commented Feb 9, 2012 at 15:30

Alex K. · Accepted Answer · 2012-02-09 15:44:29Z

4

You call document.getElementById('hhh') before hhh exists. Move it into a function you call onload.

edited Feb 9, 2012 at 15:44

Alex K.

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answered Feb 9, 2012 at 15:29

Quentin

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2 Comments

Nikhar Over a year ago

if i move there, my var a will not get decremented.

Alex K. Over a year ago

In onload call a new function that does your setup - reading a etc then have it call setInterval(startTime,600);

Alex K. · Accepted Answer · 2012-02-09 15:44:59Z

3

var a =document.getElementById('hhh').value;

This runs before the document is loaded so the underlying element may not exist in the DOM.

You call document.getElementById('hhh') before hhh exists. Move it into a function you call onload.

var a;
function setup() {
    a = document.getElementById('hhh').value;
    startTime();
}
function startTime() {
    document.getElementById('txt').innerHTML = a--;
    setInterval(startTime, 600);
}

and run setup(); in your onload.

edited Feb 9, 2012 at 15:44

answered Feb 9, 2012 at 15:30

Alex K.

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1 Comment

Nikhar Over a year ago

so how can i make it accessible without including it in the startTime(), as it won't get decremented then

Henrik Andersson · Accepted Answer · 2012-12-04 10:00:36Z

2

Leave it as an "type=input" and add the css property: display: none;

<input type="input" id="hhh" name="time" value="11" style="display: none;" />

edited Dec 4, 2012 at 10:00

Henrik Andersson

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answered Dec 4, 2012 at 9:34

Quintin

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