Image + Text swap question

[Randell D.]

Folks,
I'm still learning javascript - I've invested in a couple of books and
reading online as much as possible. I'm pretty sure what I am suggesting is
possible though I'm trying to weigh up the faults that might go with the
suggestion... all opinions welcome.

My question: I have a list of links that go to pages that have a similar
layout. Could I have a text swap, similar to what I've seen with image swaps
(or an image switch) whereby instead of loading a seperate page, text and
image is just replaced?

Other than not being accessable by non-javascript supported browsers, and
unlikely to be indexed by search engines, would I face any other
difficulties? For example, does an image/text swap have any browser
dependancy issues? If I know that all my clients will have javascript
switched on, I'm trying to figure out how much of my audience am I limiting
by having this 'feature' (my oldest clients that visit are IE5.5 and
Netscape 4 but these make up less than 2% of my entire visitors during the
past ten months).

Thanks...

 

[Lasse Reichstein Nielsen]

Folks,
I'm still learning javascript - I've invested in a couple of books and
reading online as much as possible. I'm pretty sure what I am suggesting is
possible though I'm trying to weigh up the faults that might go with the
suggestion... all opinions welcome.

My question: I have a list of links that go to pages that have a similar
layout. Could I have a text swap, similar to what I've seen with image swaps
(or an image switch) whereby instead of loading a seperate page, text and
image is just replaced?

Yes. I am not sure it is the best solution, but it is definitly technically
possible.

You have to decide on some design issues first, though.

Should all the text be loaded with the original page, or should the
new text be loaded on-demand when you click on a link? For images, it is
simple, they are always loaded when you need them, but text is not so
easily changed.

If you put the text in an iframe, you can change it by setting the src
property. It has all the problems of frames, though, and I wouldn't
recommend it for what you want.

If you fetch text on-demand, you need a way to fetch data from the
server without loading the page. Some browsers can do that with
special features like XML-Http-Request of IE and Mozilla
(<URL:http://jibbering.com/2002/4/httprequest.html>), but other browsers
need more work to fetch simple text.

If you load all the text with the original page, then switching the text
is only a matter of changing which text block is visible. Or, you can put
the text in Javascript and change the document content dynamically.

Other than not being accessable by non-javascript supported browsers, and
unlikely to be indexed by search engines, would I face any other
difficulties? For example, does an image/text swap have any browser
dependancy issues?

That depends on how you do it, and which browsers you target.

You should really decide the target browsers, and how the page should
degrade for other browsers, before anything else. It will limit what
approaches you can use.

Netscape 4 couldn't change the document structure dynmanically, but it
allowed you to change the contents of layers independently of the main
document. Other browsers that don't allow changes to the document structure
includes Opera 6, where your only choice is to load all the text at once
(or use iframes).

Text-swapping can be performed different ways:
- IE's innerHTML/innerText properties. While innerHTML is quite widely
implemented, it is non standard.
- W3C's DOM. Only supported in modern browsers, not Netscape 4 or IE 4.

If I know that all my clients will have javascript switched on,

How do you know?
Some statistics claim as many as 10% of people browsing without
Javascript.

I'm trying to figure out how much of my audience am I limiting by
having this 'feature' (my oldest clients that visit are IE5.5 and
Netscape 4 but these make up less than 2% of my entire visitors
during the past ten months).

As always, Netscape 4 is the worst offender. Not that you can blame it,
it was designed before the W3C DOM. You can blame people who still use
it and expect pages to work .

A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet?

My favorite is:
"Usenet isn't Jeopardy. The question before the answer, please."


/L

 

[Randell D.]

Yes. I am not sure it is the best solution, but it is definitly technically
possible.

You have to decide on some design issues first, though.

Should all the text be loaded with the original page, or should the
new text be loaded on-demand when you click on a link? For images, it is
simple, they are always loaded when you need them, but text is not so
easily changed.

If you put the text in an iframe, you can change it by setting the src
property. It has all the problems of frames, though, and I wouldn't
recommend it for what you want.

If you fetch text on-demand, you need a way to fetch data from the
server without loading the page. Some browsers can do that with
special features like XML-Http-Request of IE and Mozilla
(<URL:http://jibbering.com/2002/4/httprequest.html>), but other browsers
need more work to fetch simple text.

If you load all the text with the original page, then switching the text
is only a matter of changing which text block is visible. Or, you can put
the text in Javascript and change the document content dynamically.


That depends on how you do it, and which browsers you target.

You should really decide the target browsers, and how the page should
degrade for other browsers, before anything else. It will limit what
approaches you can use.

Netscape 4 couldn't change the document structure dynmanically, but it
allowed you to change the contents of layers independently of the main
document. Other browsers that don't allow changes to the document structure
includes Opera 6, where your only choice is to load all the text at once
(or use iframes).

Text-swapping can be performed different ways:
- IE's innerHTML/innerText properties. While innerHTML is quite widely
implemented, it is non standard.
- W3C's DOM. Only supported in modern browsers, not Netscape 4 or IE 4.


How do you know?
Some statistics claim as many as 10% of people browsing without
Javascript.


As always, Netscape 4 is the worst offender. Not that you can blame it,
it was designed before the W3C DOM. You can blame people who still use
it and expect pages to work .


My favorite is:
"Usenet isn't Jeopardy. The question before the answer, please."


/L

I'm curious - I knew someone with a similar name from Denmark - did you ever
work for HP?

Thanks for the prompt and detailed reply - I know my viewers have javascript
switched on because of a small clear.gif image that is downloaded
automatically, using javascript as a test. I can compare this with my
webalizer log files and things are almost the same (give or take under 2%) -
Fine for my purposes...

I do plan on offering a static 'non-javascript' version of my pages though
to cover my options....

The javascript portion includes "blurbs" - it relates to products and I
wasn't thinking of having the full text displayed - I was thinking of arrays
or objects (the latter I'm just begining to learn at the moment) to contain
the product name, the manufacturer and the first ten words (max 100chars)...
Each page refresh would change the order of the listing to give a rough
equality "top listing" thus not showing any single preference to one
manufacturer or product... I could have had it randomized via PHP but I
prefer a client-side engine...

And your Jeopardy signature - I like it and will remember it - someday it
will prove useful to me.... my girlfriend loves that show, regretably
because hearing the answer first really annoys me...

thanks for the help anyway...

 

[Lasse Reichstein Nielsen]

I'm curious - I knew someone with a similar name from Denmark - did you ever
work for HP?

Nope, sorry (I wish!). According to Krak.dk, there are 60 people in
Denmark called "Reichstein", and one other called "Lasse Reichstein",
but he lives in Copenhagen, while I'm from Århus

I know my viewers have javascript switched on because of a small
clear.gif image that is downloaded automatically, using javascript
as a test. I can compare this with my webalizer log files and things
are almost the same (give or take under 2%) - Fine for my
purposes...

That is probably a fairly accurate measure. If it is only on the front
page, it won't measure people going directly to sub pages. Still, 2%
is a fairly high number of people to annoy ...

I do plan on offering a static 'non-javascript' version of my pages though
to cover my options....

.... so this is a good idea.

The javascript portion includes "blurbs" - it relates to products and I
wasn't thinking of having the full text displayed - I was thinking of arrays
or objects (the latter I'm just begining to learn at the moment) to contain
the product name, the manufacturer and the first ten words (max 100chars)...
Each page refresh would change the order of the listing to give a rough
equality "top listing" thus not showing any single preference to one
manufacturer or product... I could have had it randomized via PHP but I
prefer a client-side engine...

Random shuffling of an array is fairly easy to do.
I don't see why you prefer clientside computation to serverside PHP.
All other things being equal, computing on the server is safer. Nobody
has PHP turned off

The description doesn't tell me whether you only load the first 100 chars
of the description, or load it all and only display the 100 char blurp.

If you only have the blurp loaded, you need to fetch the rest of the text
after the page has loaded. So, this gives you two options:
iframes (and an ilayer for NS4)
or
XMLHTTPRequest for IE and Mozilla (with some other option for other
modern browsers, and probably still an ilayer for NS4).

The most widely usable solution is iframes. It can even work without
Javascript in non-NS4 browsers.

....
<a href="productX.html" target="description" onclick="return switchTo('X')">
Product X is a fine thingie which is just what you want ...
</a>
....
<img id="imageToChange" src="prod1.png">
<iframe name="description" src="product1.html">
<ilayer name="NSdescription" src="product1.html">
</ilayer>
</iframe>
....

For NS4, you will then change "document.layers.NSdescription.src"
appropriately.

And your Jeopardy signature - I like it and will remember it

It really isn't mine. I picked it up from somebody in a Danish
newsgroup.

- someday it will prove useful to me.... my girlfriend loves that
show, regretably because hearing the answer first really annoys
me...

It's definitly just a gimmick. I can't remember the last time I saw
somebody forget to give the answer as a question.

/L