unusual behaviour

[Ken Tuck]

Hi

The following functions are working propery for IE, Ns 4.x and NS 6+ but
the image I want to display disappears in IE. Why?

function swapPic(layer,imgName,imgObj) {
o = (n &&
layer?document.layers[layer].document.images[imgName]:document.images[imgName]);
if(!o.hasswapped) o.src = eval(imgObj+".src");
}

var oRef = null;
var oRefImg = null;
function keepPic(layer,imgName,imgObj) {
if(oRef) {
// swap image back
oRef.src = oRefImg;
}
if (document.images) {
o = (n &&
layer?document.layers[layer].document.images[imgName]:document.images[imgName]);
if(o) {
oRef = o
oRefImg = o.src;
o.src = eval(imgObj+".src");
o.hasswapped = true;
}
}
}

I use the following link to chose the image I want to display

<area shape="poly" alt="" coords="25,25,21,0,30,0"
href="javascript:void(0)" title=""
onMouseOver="swapPic('metera','diala','img1');"
onClick="keepPic('metera','diala','img1');">

<div id="metera"><img src="images/pointer.aa.gif" alt="" name="diala"
id="diala" width="50" height="50" border="0" usemap="#dialita"></div>

The image map is a dial with 20 positions on it to display a position on
a dial

--
Cheers!
Ken Tuck
EyeCreate Inc.
Web Site Design | Online Applications | E-Commerce
ph: 705 755-1120
fx: 705 743-9259
http://www.eyecreate.net/

 

[Lasse Reichstein Nielsen]

The following functions are working propery for IE, Ns 4.x and NS 6+
but the image I want to display disappears in IE. Why?

That is hard to say. When asking for help, you should always supply
these three pices of infomration:

1) What are you doing? (posting or giving a link to *all* of the code
that fails, preferably by cutting down to a *minimal* example that
still exhibits the flaw. If posting code, don't let lines be more than
72 characters wide).

2) What is it supposed to do? All you say is that it is "working
properly", which means we have to guess what the code is supposed to
do (and code is *not* self explanatory, especially when it is known to
be bugged).

3) What does it do? What do you mean by "disappears"? Is it blank, is
it not in the page flow at all, or what? Be exact.

function swapPic(layer,imgName,imgObj) {

Since you didn't tell, I'll try guessing what these arguments are.

// layer - the name of a NS 4 layer if the image is inside one.
// In general, there could be more than one layer, but in practice
// it amost never happens.
// imgName - the id of the image element to change.
// imgObj - a string containing the name of a global variable.
// A very inefficient way to do it. I'll change it to contain
// the value of the variable instead.

o = (n &&
layer?document.layers[layer].document.images[imgName]:document.images[imgName]);

Long line. Luckily neither your nor my newsreader automatically break
lines.

I *assume* that "n" is a global variable that is true if the browser
is Netscape 4. It is not needed. I would make "o" a local variable instead
of global.

var o = (layer && document.layers && document.layers[layer])?
document.layers[layer].document.images[imgName]:
document.images[imgName];

if(!o.hasswapped) o.src = eval(imgObj+".src");

If you are using eval, you are probably doing something wrong.

if (!o.hasswapped) {o.src = imgObj.src;}

}

var oRef = null;

var oRefImg = null;

This is later used as the src property of an image, so a better name would
be "oRefSrc".

function keepPic(layer,imgName,imgObj) {
if(oRef) {
// swap image back
oRef.src = oRefImg;
}

if (document.images) {

Why check for document.images here, and not in the previous function.

o = (n &&
layer?document.layers[layer].document.images[imgName]:document.images[imgName]);

As above.

if(o) {
oRef = o
oRefImg = o.src;
o.src = eval(imgObj+".src");

o.src = imgObj.src;

o.hasswapped = true;
}
}
}

I use the following link to chose the image I want to display

<area shape="poly" alt="" coords="25,25,21,0,30,0"
href="javascript:void(0)" title=""
onMouseOver="swapPic('metera','diala','img1');"

onmouseover="swapPic('metera','diala',img1)"

No need to send a string containing 'img1' as an argument, if you
just use it to look up the value of the variable of that name. Just
send the value directly.

onClick="keepPic('metera','diala','img1');">
onclick="keepPic('metera','diala',img1);">

<div id="metera"><img src="images/pointer.aa.gif" alt="" name="diala"
id="diala" width="50" height="50" border="0" usemap="#dialita"></div>

/L

 

[Richard Cornford]

Ken Tuck <[email protected]> writes:

This is later used as the src property of an image, so a better
name would be "oRefSrc".

Or maybe sRefSrc if the value it is to hold is a string.

onmouseover="swapPic('metera','diala',img1)"

No need to send a string containing 'img1' as an argument, if you
just use it to look up the value of the variable of that
name. Just send the value directly.


onclick="keepPic('metera','diala',img1);">

<snip>

One of the (many) undesirable side effects of executing a javascript
pseudo-protocol URL is that some browsers stop bothering to load image
graphics after its use. Some, but not all, versions of IE exhibit that
effect.

The effect can probably be avoided by returning false from the onclick
handler to cancel the navigation in the HREF, but that makes the
javascript URL pointless as it will only be used (and predictably fail)
in the event that JavaScript is unavailable on the browser.

Richard.