Detecting what has focus

**Lee** · Jul 20 '05, 11:36 AM

Re: Detecting what has focus

Fabian said:[color=blue]
>
>Is there a way to detect which object currently has the focus in
>javascript? "this" comes close, but isnt implemented in netscape.[/color]

Sure it is:

<input id="alpha" onfocus="alert( this.id)">

**Fabian** · Jul 20 '05, 11:36 AM

Re: Detecting what has focus

Lee hu kiteb:
[color=blue]
> Fabian said:[color=green]
>>
>> Is there a way to detect which object currently has the focus in
>> javascript? "this" comes close, but isnt implemented in netscape.[/color]
>
> Sure it is:
>
> <input id="alpha" onfocus="alert( this.id)">[/color]

it seems to me that "this" is msie-specific, or at best, differently
implemented. If it wasnt, my existing script would work in netscape. It
looks like "this" doesnt work in netscape in the context of a function;
only in a html tag. How can I detect what object on screen has the focus
when a particular function is being called?

--
--
Fabian
Visit my website often and for long periods!

Sorry, the website has been stopped

http://www.lajzar.co.uk

**Lee** · Jul 20 '05, 11:36 AM

Re: Detecting what has focus

Fabian said:[color=blue]
>
>Lee hu kiteb:
>[color=green]
>> Fabian said:[color=darkred]
>>>
>>> Is there a way to detect which object currently has the focus in
>>> javascript? "this" comes close, but isnt implemented in netscape.[/color]
>>
>> Sure it is:
>>
>> <input id="alpha" onfocus="alert( this.id)">[/color]
>
>it seems to me that "this" is msie-specific, or at best, differently
>implemented. If it wasnt, my existing script would work in netscape.[/color]

There are many reasons why a script might work in one browser
but not another. The real reason isn't always obvious.
[color=blue]
>It looks like "this" doesnt work in netscape in the context of a function;
>only in a html tag. How can I detect what object on screen has the focus
>when a particular function is being called?[/color]

The "this" keyword works in the context of a function, but in
that context, it refers to the window, unless that function
is a function handler. That's true in IE and Netscape.

In this example:

function demo(ref){
document.myForm .output1.value= ref.id;
document.myForm .output2.value= this.id;
}

<form name="myForm">
<input name="output1">
<input name="output2">
<br>
<input id="alpha" onfocus="demo(t his)">
</form>

the value placed in output1 will be "alpha" and in output2 will
be "undefined" , in both IE and Netscape 7.

If demo() is actually the event handler, then the "this" keyword
will refer to the element that took focus:

<head>
<script type="text/javascript">
function demo(){
document.myForm .output1.value= this.id;
}
</script>
</head>
<body onload="documen t.myForm.alpha. onfocus=demo">
<form name="myForm">
<input name="output1">
<br>
<input id="alpha">
</form>
</body>

**Lee** · Jul 20 '05, 11:36 AM

Re: Detecting what has focus (correction)

Lee said:
[color=blue]
>The "this" keyword works in the context of a function, but in
>that context, it refers to the window, unless that function
>is a function handler. That's true in IE and Netscape.[/color]

That last line should begin "is an event handler."

**Fabian** · Jul 20 '05, 11:36 AM

Re: Detecting what has focus (correction)

Lee hu kiteb:
[color=blue]
> Lee said:
>[color=green]
>> The "this" keyword works in the context of a function, but in
>> that context, it refers to the window, unless that function
>> is a function handler. That's true in IE and Netscape.[/color]
>
> That last line should begin "is an event handler."[/color]

This is what i have now...

function Sho(ref) {
var moo = ref.parentEleme nt.id;
// broken under mozilla
alert( moo );

// show other
// var suFFix = (/_ok/i.test( moo.slice(-3) )) ? '_no' :'_ok';
// document.getEle mentById(moo.sl ice(0,-3)+suFFix).styl e.display =
'block';
// hide self
ref.parentEleme nt.style.displa y='none';
return null;
}

-

<DIV ID="1_ok" CLASS="mufti">
<A HREF="javascrip t:Xejn()" onclick="Sho(th is)">text</A></DIV>

<DIV ID="1_no">
<A HREF="javascrip t:Xejn()" onclick="Sho(th is)">text</A></DIV>

-

I have a feeling netscape cant find the parent element id because the
actual referring element (this) has no id specifically assigned. Am I on
the right track?

--
--
Fabian
Visit my website often and for long periods!

Sorry, the website has been stopped

http://www.lajzar.co.uk

**Lasse Reichstein Nielsen** · Jul 20 '05, 11:36 AM

Re: Detecting what has focus

"Fabian" <lajzar@hotmail .com> writes:
[color=blue]
> Is there a way to detect which object currently has the focus in
> javascript?[/color]

Not generally, no.

However, you can tell when an element gains the focus, because
that sets off its onfocus event handler. Not all elements can
gain focus (form controls and links are the only ones AFAIK).
[color=blue]
> "this" comes close, but isnt implemented in netscape.[/color]

"this" is a keyword that gives you the object of which the currently
executed function is a method (or the global object if there is none).

It is completely unrelated to focus. Are you sure you really mean
focus?

/L
--
Lasse Reichstein Nielsen - lrn@hotpop.com
DHTML Death Colors: <URL:http://www.infimum.dk/HTML/rasterTriangleD OM.html>
'Faith without judgement merely degrades the spirit divine.'

**Richard Cornford** · Jul 20 '05, 11:37 AM

Re: Detecting what has focus (correction)

"Fabian" <lajzar@hotmail .com> wrote in message
news:bobtfr$1cc ivs$3@ID-174912.news.uni-berlin.de...
<snip>[color=blue]
> function Sho(ref) {
> var moo = ref.parentEleme nt.id;
> // broken under mozilla[/color]
<snip>

Not broken under Mozilla, just not implemented. parentElement is part
of the Microsoft proprietary DOM. The nearest W3C DOM equivalent is
parentNode, which is implemented in IE browsers from IE 5.0 in addition
to Mozilla and most other modern browsers. parentElement can be used to
provide fall-back for IE 4, and there are some browsers that do not
implement either so some checking should be implemented within the code
rather that assuming that the function body will execute everywhere.

Richard.

**keyur shah** · Jul 20 '05, 11:37 AM

Re: Detecting what has focus

Yes, you can print this.id... it would reference the current
element/object and help u resolve ur issue.

Keyur Shah
Verizon Communications
732-423-0745

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**Thomas 'PointedEars' Lahn** · Jul 20 '05, 11:48 AM

Re: Detecting what has focus

Fabian wrote:
[color=blue]
> it seems to me that "this" is msie-specific,[/color]

No, it is part of the core language.
[color=blue]
> or at best, differently implemented. If it wasnt, my existing script
> would work in netscape. It looks like "this" doesnt work in netscape in
> the context of a function; only in a html tag.[/color]

`this' is a reference to the current context object. Within event handlers,
that is the object that triggered the event. Within methods, that is the
object that has the method as its property. Within ordinary functions, that
is the global object -- in all HTTP-UAs I know of, the current Window object.

So it probably works in the function but does not reference what you assume
it does.

HTH

PointedEars

Detecting what has focus

Detecting what has focus

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