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Detecting what has focus
Javascript JavaScript language (comp.lang.javascript)
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#1
 
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Detecting what has focus -
11-05-2003
, 06:52 AM
#2
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Is there a way to detect which object currently has the focus in javascript? "this" comes close, but isnt implemented in netscape. |
<input id="alpha" onfocus="alert(this.id)">
#3
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Fabian said: Is there a way to detect which object currently has the focus in javascript? "this" comes close, but isnt implemented in netscape. Sure it is: input id="alpha" onfocus="alert(this.id)" |
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!
http://www.lajzar.co.uk
#4
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Lee hu kiteb: Fabian said: Is there a way to detect which object currently has the focus in javascript? "this" comes close, but isnt implemented in netscape. Sure it is: input id="alpha" onfocus="alert(this.id)" it seems to me that "this" is msie-specific, or at best, differently implemented. If it wasnt, my existing script would work in netscape. |
but not another. The real reason isn't always obvious.
Quote:
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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? |
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(this)">
</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="document.myForm.alpha.onfocus=demo">
<form name="myForm">
<input name="output1">
<br>
<input id="alpha">
</form>
</body>
#5
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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. |
#6
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Lee said: 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. That last line should begin "is an event handler." |
function Sho(ref) {
var moo = ref.parentElement.id;
// broken under mozilla
alert( moo );
// show other
// var suFFix = (/_ok/i.test( moo.slice(-3) )) ? '_no' :'_ok';
// document.getElementById(moo.slice(0,-3)+suFFix).style.display =
'block';
// hide self
ref.parentElement.style.display='none';
return null;
}
-
<DIV ID="1_ok" CLASS="mufti">
<A HREF="javascript:Xejn()" onclick="Sho(this)">text</A></DIV>
<DIV ID="1_no">
<A HREF="javascript:Xejn()" onclick="Sho(this)">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!
http://www.lajzar.co.uk
#7
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Is there a way to detect which object currently has the focus in javascript? |
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).
Quote:
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"this" comes close, but isnt implemented in netscape. |
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 (AT) hotpop (DOT) com
DHTML Death Colors: <URL:http://www.infimum.dk/HTML/rasterTriangleDOM.html>
'Faith without judgement merely degrades the spirit divine.'
#8
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function Sho(ref) { var moo = ref.parentElement.id; // broken under mozilla 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.
#9
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#10
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it seems to me that "this" is msie-specific, |
Quote:
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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. |
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
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