Develop Reference

Insert a logo next to any DOM element

I'm developing a Firefox extension which amends the contents of a loaded webpage. First I select all the elements of which the "src" or "href" attributes match my regex (this part of the code works).
Then, I would like to place a little image at the top right corner of the found element's parent using the following code:
/* create and add attributes to image */
var img = window.content.document.createElement("img");
var b = window.content.document.createAttribute("src");
b.nodeValue = "chrome://plugin/content/agent.png";
img.setAttributeNode(b);
img.addEventListener("click", function(){ alert("ds"); });
img.style.display = "block";
img.style.border = "3px solid red";
img.style.position = "relative";
img.style.top = "-10px";
img.style.right = "-10px";
img.style.left = "20px";
// ... the code to return the element...
//now insert the image
$jq(img).appendTo(element.parentNode);
The current result is that either the image is shown just at the bottom of the element's parent or not shown at all.
If you look at this: http://jsfiddle.net/yzwh5/64/ - I would like my button to work in a similar manner to that red cross.

You must "play" with the element's CSS positioning, in fact it doesn't matter where do you insert the images, but where you do position them.
Maybe you would like to take a look at "next-to", a jQuery plugin that automates the calculations to position an element next to another element
For example:
<script type="text/javascript">
$('.PlaceThisDiv').nextTo($('.ThisOtherDiv'), {position:'right', shareBorder:'top'});
</script>
As you can see in this Fiddle i have prepared (contains the plugin itself)
http://jsfiddle.net/PvcNr/
you will get you something like this:
More info: https://code.google.com/p/next-to/
Hope it helps

Try CSS code like this:
.my-ext-overlay:after {
content:url(smiley.gif);
position: absolute;
margin-left: -16px; margin-top: -16px;
}
and then adding the ".my-ext-overlay" class name to each element you find.
See example

Firstly, CSS floats are called cssFloat (or htmlFloat in some browsers) because float is a reserved word. Second, there is no such float value as block.
Third, you missed an x in -10px for the right property.
Fourth, setting both relative left and right positions can lead to unexpected behaviour.
Fifth, you shouldn't use createAttribute, since attribute nodes aren't reliable in all browsers. Instead, use setAttribute on the element.
Sixth, if this did work it would mess up page layout around the element you're searching for, so you would be better off with position: absolute so it doesn't affect the flow. If you do this, however, you should use margin-left instead of left (same for other directions), to shift the element around.
I think that should at least get the thing close to working...

Javascript Arranging Images as Pile of Cards

Im new to javascript so im sure there is a lot i am missing in its understanding.
What i am trying to do it create a layer of images so that it looks like a pile of cards.
have seen similar codes and have tried to follow their idea but i just cant get the images to position properly. All 10 or so images are place in the exact same location.
Can any help to see why they not positioning? Also what is "em". I cant find any literature on it but assume it is the measurement em like px ?? Why is it in "" ?
function Display() {
var el;
var left = 0;
var top = 0;
var i=0;
var n = deck.length;
var cardNode;
var img = document.createElement("IMG");
img.src = "wendell7_back.png";
el = document.getElementById('deck');
el.appendChild(img);
while (el.firstChild != null) el.removeChild(el.firstChild);
for (i = 0; i < Math.round(n / 5); i++)
{
cardNode = document.createElement("DIV");
cardNode.appendChild(img);
cardNode.style.left = left + "em";
cardNode.style.top = top + "em";
el.appendChild(cardNode);
left += 0.1;
top += 0.1;
}
}

"em" is the width of an "M" in whichever font is being used (or browser's default font if nothing overrides it).
There are at least two things wrong in your code:
left and top have no meaning unless the element to which they are applied also has position:absolute or position:relative (or position:fixed I think). Your safest approach is to apply position:relative (but no left: or top:) to the container and position:absolute to each of the cards.
There's only one img. For multiple cards, you need multiple imgs otherwise the same img gets repositioned over and over.
A more economical approach is probably to show a separate "stack" image for multiple cards and single card images for a single cards.
An even more economical approach is only to show single card images with a "tooltip" to indicate the number of cards in a stack. I have successfully employed this technique in an implementation of a game of patients.
Of course, these alternative techniques don't work if you want to show multiple cards as a "fanned out" stack of upturned cards.
Create a class and modify the position of that for the deck. Here is the working code:
function Display() {
var el;
var left = 0;
var top = 0;
var i=0;
var n = deck.length;
var cardNode;
el = document.getElementById('deck');
while (el.firstChild != null) el.removeChild(el.firstChild);
for (i = 0; i < Math.round(n / 5); i++)
{
cardNode = document.createElement("DIV");
cardNode.className = "card2";
var img = document.createElement("IMG");
img.src = "wendell7_back.png";
cardNode.appendChild(img);
cardNode.style.left = left + "em";
cardNode.style.top = top + "em";
el.appendChild(cardNode);
left += .1;
top -= 6.2;
}
}
Hope this will help.

There are a couple of problems with that code.
You're only using one img, and then you're appending it to each div you create. When you append an element to another element, if it's already in the DOM tree, you end up moving it. What you need is to create a separate img element for each card.
You haven't shown us your CSS, but unless you're using CSS to make all div elements under the #deck element absolutely or relatively positioned, the left and top style attributes will be ignored, as the div will be subject to normal flow.
Also what is "em". I cant find any literature on it but assume it is the measurement em like px ??
Yes, it's a term from typography. An "em" is the width of a capital letter M.
Why is it in "" ?
Because it's a string. You'd also have to have "px" in quotes. What you're doing with this code:
cardNode.style.left = left + "em";
...is using JavaScript to set a style property. Style properties are always strings, in this case you're creating strings like "0.1em" and "0.2em", etc.
Some reading:
DOM2 Core specification
DOM2 HTML specification
DOM3 Core specification
HTML5 specification
Various CSS specifications
A good book on JavaScript, I quite liked JavaScript: The Definitive Guide by David Flanagan
A good book on CSS and HTML authoring

My guess is that your offset is too small: if you replace the "em" with "px" for test's sake, and increase the left and top variables by 10 instead of 0.1, I bet you'll see some results.
To explain the em: 1em is equal to the current font-size of the element. If you haven't set the font size it uses the browser default. If you set the font-size to be e.g. 20px on the body tag, then 1em will equal 20px.

Make sure that your 'cards' have the css property 'position' set - either to 'absolute' or 'relative'.

Truncating html text appropriately into a fixed size area

In a generated html page, we have a fixed size area (lets say 200 x 300) in which we need to fit in as much text as possible (like a regular paragraph of text), and if it doesn't fit, remove an appropriate number of characters and append "..." to the end.
The text is NOT in a fixed sized font, and although we are using one specific font for this text, a "generic" solution would obviously be preferred.
This looked interesting, but I'm thinking it would be very slow with this function being called for several items on a page - http://bytes.com/topic/javascript/answers/93847-neatly-truncating-text-fit-physical-dimension
The solution can use an intermix of html, css, js, and php as needed.
Suggestions on approaches are more than welcome!

I'd say that the solution you found is the best. It is, for instance, used for this jQuery plugin which autoresizes textareas as you enter text into it. I took the concept and rewrote it with jQuery for this simple test here: http://jsfiddle.net/ZDr5K/
var para = $('#para');
var height = 200;
while(para.height() >= height){
var text = para.text();
para.text(text.substring(0, text.length - 4) + '...');
}
Possible improvements would include right trimming and removing the period if the last character is a full stop. Removing word by word would also be more readable/slightly faster.
As for the function running multiple times, that would be unavoidable. The only thing you can really do with CSS here is to use :after to append the ellipses, but even that should be avoided for cross-compatibility problems.

Set the element dimensions via CSS and its overflow to "hidden".
Then, find out with this function, if the element's content is overflowing (via):
// Determines if the passed element is overflowing its bounds,
// either vertically or horizontally.
// Will temporarily modify the "overflow" style to detect this
// if necessary.
function checkOverflow(el)
{
var curOverflow = el.style.overflow;
if ( !curOverflow || curOverflow === "visible" )
el.style.overflow = "hidden";
var isOverflowing = el.clientWidth < el.scrollWidth
|| el.clientHeight < el.scrollHeight;
el.style.overflow = curOverflow;
return isOverflowing;
}
Now, in a loop remove text and check until it is not overflowing anymore. Append an ellipsis character (String.fromCharCode(8230)) to the end, but only if it was overflowing.
To avoid any flickering effects during that operation, you can try working on a hidden copy of the element, but I'm not sure if the browsers do the necessary layout calculations on an element that's not visible. (Can anyone clarify that?)

Jquery - Truncate Text by Line (not by character count)

I need a Jquery script to truncate a text paragraph by line (not by character count).
I would like to achieve an evenly truncated text-block. It should have a "more" and "less" link to expand and shorten the text paragraph. My text paragraph is wrapped in a div with a class, like this:
<div class="content">
<h2>Headline</h2>
<p>The paragraph Text here</p>
</div>
The closest solution i could find on SOF is the one below (but it`s for textarea element and does not work for me):
Limiting number of lines in textarea
Many thanks for any tips.
Ben

For a basic approach, you could take a look at the line-height CSS property and use that in your calculations. Bear in mind that this approach will not account for other inline elements that are larger than that height (e.g. images).
If you want something a bit more advanced, you can get the information about each line using getClientRects() function. This function returns a collection of TextRectangle objects with width, height and offset for each one.
See this answer here for an example (albeit an unrelated goal) of how getClientRects() works.
Update, had a bit of time to come back and update this answer with an actual example. It's basic, but you get the idea:
http://jsbin.com/ukaqu3/2
A couple of pointers:
The collection returned by getClientRects is static, it won't update automatically if the containing element's dimensions change. My example works around this by capturing the window's resize event.
For some strange standards-compliance reason that I'm not understanding, the element you call getClientRects on must be an inline element. In the example I have, I use a container div with the text in another div inside with display: inline.

I made this little jQuery code to allow me truncate text blocks by line (via CSS classes), feel free to use and comment it.
Here is the jsFiddle, which also include truncate functions by char count or word count. You can see that currently, resize the window won't refresh the block display, I'm working on it.
/*
* Truncate a text bloc after x lines
* <p class="t_truncate_l_2">Lorem ipsum magna eiusmod sit labore.</p>
*/
$("*").filter(function () {
return /t_truncate_l_/.test($(this).attr('class'));
}).each(function() {
var el = $(this);
var content = el.text();
var classList = el.attr('class').split(/\s+/);
$.each(classList, function(index, item){
if(/^t_truncate_l_/.test(item)) {
var n = item.substr(13);
var lineHeight = parseInt(el.css('line-height'));
if(lineHeight == 1 || el.css('line-height') == 'normal')
lineHeight = parseInt(el.css('font-size')) * 1.3;
var maxHeight = n * lineHeight;
var truncated = $.trim(content);
var old;
if(el.height() > maxHeight)
truncated += '...';
while(el.height() > maxHeight && old != truncated) {
old = truncated;
truncated = truncated.replace(/\s[^\s]*\.\.\.$/, '...');
el.text(truncated);
}
}
});
});

why not make the p element with overflow: hidden; give fixed line height, caluclate the height of the div so id contains exactly the number of lines you require and the only change the height of the p from javascript.
p{
overflow:hidden;
line-height:13px;
height:26px; /* show only 2 rows */
}
<script type="text/javascript">
function seeMoreRows(){
$(p).height("52px");
}
</script>

I made a small module that works with pure text content, no nested tags and no css-padding on the text-containing element is allowed (but this functionality could easily be added).
The HTML:
<p class="ellipsis" data-ellipsis-max-line-count="3">
Put some multiline text here
</p>
The Javascript/Jquery:
( function() {
$(document).ready(function(){
store_contents();
lazy_update(1000);
});
// Lazy update saves performance for other tasks...
var lazy_update = function(delay) {
window.lazy_update_timeout = setTimeout(function(){
update_ellipsis();
$(window).one('resize', function() {
lazy_update(delay);
});
}, delay);
}
var store_contents = function(){
$('.ellipsis').each(function(){
var p = $(this);
p.data('ellipsis-storage', p.html());
});
}
var update_ellipsis = function(){
$('.ellipsis').each(function(){
var p = $(this);
var max_line_count = p.data('ellipsis-max-line-count');
var line_height = p.html('&nbsp').outerHeight();
var max_height = max_line_count*line_height;
p.html(p.data('ellipsis-storage'));
var p_height = p.outerHeight();
while(p_height > max_height){
var content_arr = p.html().split(' ');
content_arr.pop();
content_arr.pop();
content_arr.push('...');
p.html(content_arr.join(' '));
p_height = p.outerHeight();
}
});
}
} )();
I hope you like it!

If you used a monospaced font, you'd have a shot at this working, as you'd have a good idea how many letters fit onto each line, for an element of a defined width. However, if a word breaks across lines, then this might get tricky..
e: found another question which is basically what you're after - they didn't really have a resolution either, but to my mind, the line-height and element height seems closest.
"How can I count text lines inside a dom element"

tl;dr - set a height on your container div and then use the jQuery dotdotdot plugin
Was about to make #Andy E's awesome example into a plugin, but then realized https://github.com/BeSite/jQuery.dotdotdot could pull this off. Our use case is we want to show one line on desktop widths and two lines on mobile/tablet.
Our CSS will just set the container div to the equivalent of one or two line-height's accordingly and then the dotdotdot plugin appears to handle the rest.

Div absolute position relative to static elements

I have a div element which I'm using as a pop-over search field which I want to have appear under the element which is being filtered. However, it seems that I cannot use the style.bottom and style.left of the element I want the field to be relative to as this element is static.
Example is here: http://www.is-epic.co.uk/example/example.html
Clicking the Header 2 link will have the input box appear, in the top-left corner of the table. I would like it to appear roughly where Data 1.2 is. How do I achieve this?
(Code in example.html is on one page, in live dev CSS and JS are in separate files)

Set the element you wish to position the other element with respect to to position: relative.
This will make it the containing block for any descendants that are position: absolute (unless an element between the two is also position: not static).

this works in FF and Google-Chrome
var head = document.getElementById("header_2");
var filter = document.getElementById("search_filter");
filter.style.display = "";
filter.style.left = head.offsetLeft + 'px';
filter.style.top = head.offsetTop + head.offsetHeight + 'px';
it should work with IE as well..
i used variables filter and head to cut down on typing :)

The problem is that for header_2 both style.left and style.bottom are 0, so that
document.getElementById("search_filter").style.left =
document.getElementById("header_2").style.left;
document.getElementById("search_filter").style.top =
document.getElementById("header_2").style.bottom;
is equivalent to
document.getElementById("search_filter").style.left = 0;
document.getElementById("search_filter").style.top = 0;
which is exactly what happens. You have to find out header_2's actual position, e.g. using jQuery.