Now that Microsoft has decided to move the #-ms-viewport rule in Edge behind an about:config flag, using javascript (not jquery) how do you determine if the user has that flag enabled (or is using an older version of Edge where it was still supported)?
Thread about the withdrawal of the rule here https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/7970618/
Maybe something like this? Please see comments in code.
function testSupportMsViewport() {
let result = false;
let s = document.createElement('style');
let test = document.createElement('div');
// create style rule to make viewport 200px in width
// if #-ms-viewport is interpreted
s.innerHTML = '#-ms-viewport { width: 200px; }';
// hide any overflow hence we do not need to take scrollbars into account
s.innerHTML += '* { overflow-y: hidden; }';
// use fixed position, block box sizing and no paddings/margins/borders
// together with a width of 1% (which is 2px when the viewport is 200px)
s.innerHTML += '.foo { position: fixed; display: block; padding: 0; border: 0; margin: 0; width: 1%; }';
test.classList += 'foo';
// append the style element and the test div to the html element
// applying the test styles to the div
// note that we're not appending it to body since there may be
// styles applied which could disturb calculations
document.documentElement.appendChild(s);
document.documentElement.appendChild(test);
// check width of test div. If the browser interprets the rule,
// it should be 2 (2px)
// obviously, this yields a false-positive when the viewport really is just 200px in width. Think about using some other value or add additional checks
if (parseFloat(window.getComputedStyle(test).width) === 2) {
result = true;
}
// Remove elements since they're not needed anymore
document.documentElement.removeChild(s);
document.documentElement.removeChild(test);
return result;
}
I was not able to test that snippet in Edge since I'm not using Windows. However, the function returns true if the viewport is 200px in width and false otherwise.
(If you're targeting ES5, you may replace the let by var)
Related
This question already has answers here:
How can I force WebKit to redraw/repaint to propagate style changes?
(33 answers)
Closed 4 years ago.
Currently I am working on an animation for a website which involves two elements having their position changed over a period of time and usually reset to their initial position. Only one element will be visible at a time and everything ought to run as smoothly as possible.
Before you ask, a CSS-only solution is not possible as it is dynamically generated and must be synchronised. For the sake of this question, I will be using a very simplified version which simply consists of a box moving to the right. I shall be referring only to this latter example unless explicitly stated for the remainder of this question to keep things simple.
Anyway, the movement is handled by the CSS transition property being set so that the browser can do the heavy lifting for that. This transition must then be done away with in order to reset the element's position in an instant. The obvious way of doing so would be to do just that then reapply transition when it needs to get moving again, which is also right away. However, this isn't working. Not quite. I'll explain.
Take a look at the JavaScript at the end of this question or in the linked JSFiddle and you can see that is what I'm doing, but setTimeout is adding a delay of 25ms in between. The reason for this is (and it's probably best you try this yourself) if there is either no delay (which is what I want) or a very short delay, the element will either intermittently or continually stay in place, which isn't the desired effect. The higher the delay, the more likely it is to work, although in my actual animation this causes a minor jitter because the animation works in two parts and is not designed to have a delay.
This does seem like the sort of thing that could be a browser bug but I've tested this on Chrome, Firefox 52 and the current version of Firefox, all with similar results. I'm not sure where to go from here as I have been unable to find this issue reported anywhere or any solutions/workarounds. It would be much appreciated if someone could find a way to get this reliably working as intended. :)
Here is the JSFiddle page with an example of what I mean.
The markup and code is also pasted here:
var box = document.getElementById("box");
//Reduce this value or set it to 0 (I
//want rid of the timeout altogether)
//and it will only function correctly
//intermittently.
var delay = 25;
setInterval(function() {
box.style.transition = "none";
box.style.left = "1em";
setTimeout(function() {
box.style.transition = "1s linear";
box.style.left = "11em";
}, delay);
}, 1000);
#box {
width: 5em;
height: 5em;
background-color: cyan;
position: absolute;
top: 1em;
left: 1em;
}
<div id="box"></div>
Force the DOM to recalculate itself before setting a new transition after reset. This can be achieved for example by reading the offset of the box, something like this:
var box = document.getElementById("box");
setInterval(function(){
box.style.transition = "none";
box.style.left = "1em";
let x = box.offsetLeft; // Reading a positioning value forces DOM to recalculate all the positions after changes
box.style.transition = "1s linear";
box.style.left = "11em";
}, 1000);
body {
background-color: rgba(0,0,0,0);
}
#box {
width: 5em;
height: 5em;
background-color: cyan;
position: absolute;
top: 1em;
left: 1em;
}
<div id="box"></div>
See also a working demo at jsFiddle.
Normally the DOM is not updated when you set its properties until the script will be finished. Then the DOM is recalculated and rendered. However, if you read a DOM property after changing it, it forces a recalculation immediately.
What happens without the timeout (and property reading) is, that the style.left value is first changed to 1em, and then immediately to 11em. Transition takes place after the script will be fihished, and sees the last set value (11em). But if you read a position value between the changes, transition has a fresh value to go with.
Instead of making the transition behave as an animation, use animation, it will do a much better job, most importantly performance-wise and one don't need a timer to watch it.
With the animation events one can synchronize the animation any way suited, including fire of a timer to restart or alter it.
Either with some parts being setup with CSS
var box = document.getElementById("box");
box.style.left = "11em"; // start
box.addEventListener("animationend", animation_ended, false);
function animation_ended (e) {
if (e.type == 'animationend') {
this.style.left = "1em";
}
}
#box {
width: 5em;
height: 5em;
background-color: cyan;
position: absolute;
top: 1em;
left: 1em;
animation: move_me 1s linear 4;
}
#keyframes move_me {
0% { left: 1em; }
}
<div id="box"></div>
Or completely script based
var prop = 'left', value1 = '1em', value2 = '11em';
var s = document.createElement('style');
s.type = 'text/css';
s.innerHTML = '#keyframes move_me {0% { ' + prop + ':' + value1 +' }}';
document.getElementsByTagName('head')[0].appendChild(s);
var box = document.getElementById("box");
box.style.animation = 'move_me 1s linear 4';
box.style.left = value2; // start
box.addEventListener("animationend", animation_ended, false);
function animation_ended (e) {
if (e.type == 'animationend') {
this.style.left = value1;
}
}
#box {
width: 5em;
height: 5em;
background-color: cyan;
position: absolute;
top: 1em;
left: 1em;
}
<div id="box"></div>
This question already has answers here:
How do I get the (x, y) pixel coordinates of the caret in text boxes?
(2 answers)
Closed 8 years ago.
In my project I'm trying to get the offset position of the caret in a textarea in pixels. Can this be done?
Before asking here, I have gone through many links, especially Tim Down's, but I couldn't find a solution which works in IE8+, Chrome and Firefox. It seems Tim Down is working on this.
Some other links which I have found have many issues like not finding the top offset of the caret position.
I am trying to get the offset position of the caret because I want to show an auto-complete suggestion box inside the textarea by positioning it based on the offset position of the caret.
PS: I can't use a contenteditable div because I have written lots of code related to a textarea.
You can create a separate (invisible) element and fill it with textarea content from start to the cursor position. Textarea and the "clone" should have matching CSS (font properties, padding/margin/border and width). Then stack these elements on top of each other.
Let me start with a working example, then walk through the code: http://jsfiddle.net/g7rBk/
Updated Fiddle (with IE8 fix)
HTML:
<textarea id="input"></textarea>
<div id="output"><span></span></div>
<div id="xy"></div>
Textarea is self-explanatory. Output is a hidden element to which we'll pass text content and make measures. What's important is that we'll use an inline element. the "xy" div is just an indicator for testing purposes.
CSS:
/* identical styling to match the dimensions and position of textarea and its "clone"
*/
#input, #output {
position:absolute;
top:0;
left:0;
font:14px/1 monospace;
padding:5px;
border:1px solid #999;
white-space:pre;
margin:0;
background:transparent;
width:300px;
max-width:300px;
}
/* make sure the textarea isn't obscured by clone */
#input {
z-index:2;
min-height:200px;
}
#output {
border-color:transparent;
}
/* hide the span visually using opacity (not display:none), so it's still measurable; make it break long words inside like textarea does. */
#output span {
opacity:0;
word-wrap: break-word;
overflow-wrap: break-word;
}
/* the cursor position indicator */
#xy {
position:absolute;
width:4px;
height:4px;
background:#f00;
}
JavaScript:
/* get references to DOM nodes we'll use */
var input = document.getElementById('input'),
output = document.getElementById('output').firstChild,
position = document.getElementById('position'),
/* And finally, here it goes: */
update = function(){
/* Fill the clone with textarea content from start to the position of the caret. You may need to expand here to support older IE [1]. The replace /\n$/ is necessary to get position when cursor is at the beginning of empty new line.
*/
output.innerHTML = input.value.substr( 0, input.selectionStart ).replace(/\n$/,"\n\001");
/* the fun part!
We use an inline element, so getClientRects[2] will return a collection of rectangles wrapping each line of text.
We only need the position of the last rectangle.
*/
var rects = output.getClientRects(),
lastRect = rects[ rects.length - 1 ],
top = lastRect.top - input.scrollTop,
left = lastRect.left+lastRect.width;
/* position the little div and see if it matches caret position :) */
xy.style.cssText = "top: "+top+"px;left: "+left+"px";
}
[1] Caret position in textarea, in characters from the start
[2] https://developer.mozilla.org/en/docs/DOM/element.getClientRects
Edit: This example only works for fixed-width textarea. To make it work with user-resizable textarea you'd need to add an event listener to the resize event and set the #output dimensions to match new #input dimensions.
Here's an approach using rangyinputs, rangy and jQuery.
It basically copies the whole text from inside the textarea into a div of the same size. I have set some CSS to ensure that in every browser, the textarea and the div wrap their content in exactly the same way.
When the textarea is clicked, I read out at which character index the caret is positioned, then I insert a caret span at the same index inside the div. By only doing that I ended up having an issue with the caret span jumping back to the previous line if the user clicked at the start of a line. To fix that I check if the previous character is a space (which would allow a wrap to occur), if that is true, I wrap it in a span, and I wrap the next word (the one directly after the caret position) in a span. Now I compare the top values between these two span's, if they differ, there was some wrapping going on, so I assume that the top and the left value of the #nextword span are equivalent to the caret position.
This approach can still be improved upon, I'm sure I haven't thought of everything that could possibly go wrong, and even if I have, then I haven't bothered implementing a fix for all of them as I don't have the time to do so at the moment, a number of things that you would need to look at:
it doesn't yet handle hard returns inserted with Enter (fixed)
positioning breaks when entering multiple spaces in a row (fixed)
I think hyphens would allow a content wrap to occur as well..
Currently it works exactly the same way across browsers here on Windows 8 with the latest versions of Chrome, Firefox, IE and Safari. My testing has not been very rigorous though.
Here's a jsFiddle.
I hope it will help you, at the very least it might give you some ideas to build on.
Some Features:
I have included a ul for you which is positioned in the right spot, and fixed a Firefox issue where the textarea selection was not re-set back to its original spot after the DOM manipulations.
I have added IE7 - IE9 support and fixed the multiple word selection issue pointed out in the comments.
I have added support for hard returns inserted with Enter and multiple spaces in a row.
I have fixed an issue with the default behaviour for the ctrl+shift+left arrow text selection method.
JavaScript
function getTextAreaXandY() {
// Don't do anything if key pressed is left arrow
if (e.which == 37) return;
// Save selection start
var selection = $(this).getSelection();
var index = selection.start;
// Copy text to div
$(this).blur();
$("div").text($(this).val());
// Get current character
$(this).setSelection(index, index + 1);
currentcharacter = $(this).getSelection().text;
// Get previous character
$(this).setSelection(index - 1, index)
previouscharacter = $(this).getSelection().text;
var start, endchar;
var end = 0;
var range = rangy.createRange();
// If current or previous character is a space or a line break, find the next word and wrap it in a span
var linebreak = previouscharacter.match(/(\r\n|\n|\r)/gm) == undefined ? false : true;
if (previouscharacter == ' ' || currentcharacter == ' ' || linebreak) {
i = index + 1; // Start at the end of the current space
while (endchar != ' ' && end < $(this).val().length) {
i++;
$(this).setSelection(i, i + 1)
var sel = $(this).getSelection();
endchar = sel.text;
end = sel.start;
}
range.setStart($("div")[0].childNodes[0], index);
range.setEnd($("div")[0].childNodes[0], end);
var nextword = range.toHtml();
range.deleteContents();
var position = $("<span id='nextword'>" + nextword + "</span>")[0];
range.insertNode(position);
var nextwordtop = $("#nextword").position().top;
}
// Insert `#caret` at the position of the caret
range.setStart($("div")[0].childNodes[0], index);
var caret = $("<span id='caret'></span>")[0];
range.insertNode(caret);
var carettop = $("#caret").position().top;
// If preceding character is a space, wrap it in a span
if (previouscharacter == ' ') {
range.setStart($("div")[0].childNodes[0], index - 1);
range.setEnd($("div")[0].childNodes[0], index);
var prevchar = $("<span id='prevchar'></span>")[0];
range.insertNode(prevchar);
var prevchartop = $("#prevchar").position().top;
}
// Set textarea selection back to selection start
$(this).focus();
$(this).setSelection(index, selection.end);
// If the top value of the previous character span is not equal to the top value of the next word,
// there must have been some wrapping going on, the previous character was a space, so the wrapping
// would have occured after this space, its safe to assume that the left and top value of `#nextword`
// indicate the caret position
if (prevchartop != undefined && prevchartop != nextwordtop) {
$("label").text('X: ' + $("#nextword").position().left + 'px, Y: ' + $("#nextword").position().top);
$('ul').css('left', ($("#nextword").position().left) + 'px');
$('ul').css('top', ($("#nextword").position().top + 13) + 'px');
}
// if not, then there was no wrapping, we can take the left and the top value from `#caret`
else {
$("label").text('X: ' + $("#caret").position().left + 'px, Y: ' + $("#caret").position().top);
$('ul').css('left', ($("#caret").position().left) + 'px');
$('ul').css('top', ($("#caret").position().top + 14) + 'px');
}
$('ul').css('display', 'block');
}
$("textarea").click(getTextAreaXandY);
$("textarea").keyup(getTextAreaXandY);
HTML
<div></div>
<textarea>Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book.</textarea>
<label></label>
<ul>
<li>Why don't you type this..</li>
</ul>
CSS
body {
font-family: Verdana;
font-size: 12px;
line-height: 14px;
}
textarea, div {
font-family: Verdana;
font-size: 12px;
line-height: 14px;
width: 300px;
display: block;
overflow: hidden;
border: 1px solid black;
padding: 0;
margin: 0;
resize: none;
min-height: 300px;
position: absolute;
-moz-box-sizing: border-box;
white-space: pre-wrap;
}
span {
display: inline-block;
height: 14px;
position: relative;
}
span#caret {
display: inline;
}
label {
display: block;
margin-left: 320px;
}
ul {
padding: 0px;
margin: 9px;
position: absolute;
z-index: 999;
border: 1px solid #000;
background-color: #FFF;
list-style-type:none;
display: none;
}
#media screen and (-webkit-min-device-pixel-ratio:0) {
span {
white-space: pre-wrap;
}
}
div {
/* Firefox wrapping fix */
-moz-padding-end: 1.5px;
-moz-padding-start: 1.5px;
/* IE8/IE9 wrapping fix */
padding-right: 5px\0/;
width: 295px\0/;
}
span#caret
{
display: inline-block\0/;
}
There's a much simpler solution for getting the caret position in pixels, than what's been presented in the other answers.
Note that this question is a duplicate of a 2008 one, and I've answered it here. I'll only maintain the answer at that link, since this question should have been closed as duplicate years ago.
Copy of the answer
I've looked for a textarea caret coordinates plugin for meteor-autocomplete, so I've evaluated all the 8 plugins on GitHub. The winner is, by far, textarea-caret-position from Component.
Features
pixel precision
no dependencies whatsoever
browser compatibility: Chrome, Safari, Firefox (despite two bugs it has), IE9+; may work but not tested in Opera, IE8 or older
supports any font family and size, as well as text-transforms
the text area can have arbitrary padding or borders
not confused by horizontal or vertical scrollbars in the textarea
supports hard returns, tabs (except on IE) and consecutive spaces in the text
correct position on lines longer than the columns in the text area
no "ghost" position in the empty space at the end of a line when wrapping long words
Here's a demo - http://jsfiddle.net/dandv/aFPA7/
How it works
A mirror <div> is created off-screen and styled exactly like the <textarea>. Then, the text of the textarea up to the caret is copied into the div and a <span> is inserted right after it. Then, the text content of the span is set to the remainder of the text in the textarea, in order to faithfully reproduce the wrapping in the faux div.
This is the only method guaranteed to handle all the edge cases pertaining to wrapping long lines. It's also used by GitHub to determine the position of its # user dropdown.
JsFiddle of working example: http://jsfiddle.net/42zHC/2/
Basically, we figure out how many columns fit in the width (since it will be monospace). We have to force scrollbars to always be there otherwise the calculation is off. Then we divide the number of columns that fit with the width, and we get the x offset per character. Then we set the line height on the textarea. Since we know how many characters are in a row, we can divide that with the number of characters and we get the row number. With the line height, we now have the y offset. Then we get the scrollTop of the textarea and subtract that, so that once it starts using the scrollbar, it still shows up in the right position.
Javascript:
$(document).ready(function () {
var cols = document.getElementById('t').cols;
var width = document.getElementById('t').clientWidth;
var height = $('textarea').css('line-height');
var pos = $('textarea').position();
$('#t').on('keyup', function () {
el = document.getElementById("t");
if (el.selectionStart) {
selection = el.selectionStart;
} else if (document.selection) {
el.focus();
var r = document.selection.createRange();
if (r == null) {
selection = 0;
}
var re = el.createTextRange(),
rc = re.duplicate();
re.moveToBookmark(r.getBookmark());
rc.setEndPoint('EndToStart', re);
selection = rc.text.length;
} else { selection = 0 }
var row = Math.floor((selection-1) / cols);
var col = (selection - (row * cols));
var x = Math.floor((col*(width/cols)));
var y = (parseInt(height)*row);
$('span').html("row: " + row + "<br>columns" + col + "<br>width: " + width + "<br>x: " + x +"px<br>y: " + y +"px<br>Scrolltop: "+$(this).scrollTop()).css('top',pos.top+y-$(this).scrollTop()).css('left',pos.left+x+10);
});
});
HTML:
<textarea id="t"></textarea>
<br>
<span id="tooltip" style="background:yellow"></span>
CSS:
textarea {
height: 80px;
line-height: 12px;
overflow-y:scroll;
}
span {
position: absolute;
}
I couldn't get something similar to work, so my solution was to locate the character position of the caret in the textarea, cut out the current paragraph and display this next to the textarea.
Using the offset, I placed a fake cursor (div, display:inline, 1px wide, border-left: 1px solid black) in this view of the editable text.
This way, you can create a visual feedback area where you can show the result of effects (quite like stackoverflow does when you write an answer).
I am trying to learn a few things without jQuery. Here is one of the challenges I'm facing.
I have a fixed contenteditable div that when adding text to the div, if the scrollHeight exceeds the clientHeight I shrink the font until content fits the div.
Occasionally I "rebuild" the text which replaces the innerHTML programmatically. Or the user can delete text which should reduce the scrollHeight, but in both cases, the scrollHeight remains the maximum value. I need some way to increase the font size to "fit" the div again. (that ideally isn't super expensive)
Example:
My clientHeight = 142, and the scrollHeight = 158. A loop reduces the font size, until scrollHeight is 142.
Then, the user deletes a line of text, but the scrollHeight is still 142, no change.
code to reduce/increase height:
var textBox = document.getElementById('text');
var current, min = 6, max = 14;
current = textBox.style.fontSize.substr(0, textBox.style.fontSize.length - 2);
current = parseInt(current);
if (textBox.clientHeight < textBox.scrollHeight) {
while (textBox.clientHeight < textBox.scrollHeight) {
current--;
if (current < min) break;
textBox.style.fontSize = '' + current + 'pt';
}
} else if (textBox.clientHeight > textBox.scrollHeight) {
while (textBox.clientHeight > textBox.scrollHeight) {
current++;
if (current > max) break;
textBox.style.fontSize = '' + current + 'pt';
}
}
html (incase it matters):
<div id="text" contenteditable="true"></div>
css (incase it matters):
#text {
position: relative;
border: 1px solid blue;
top: 180px;
left: 31px;
width: 300px;
height: 132px;
padding: 5px;
font-family: 'mplantin';
font-size: 14pt;
font-weight: 200;
}
I was on the same boat, but with an iframe; I'm not sure if my solution suits your chat window because its for page transitioning, but after some testing this is my hack. "content" is the id of an iframe and this is executed inside a javascript function that is called when the page change is needed:
var c=document.getElementById("content");
c.width=0;
c.height=0;
c.src="page.html";
the `src' assignment method expands the values set to 0 right after, achieving the desired result; there may be a way for you to constantly re-size a text area like that; however, I had visual issues with you; I ended up using timers so that the change would take place while the transition between pages was transparent.
This seemed to fix my issue:
element.style.height = "auto";
both answers from #nixahn and #jeff are working for me (chrome,ff)
iframe.style.height ="0"; // or "auto"
iframe.contentWindow.document.open();
iframe.contentWindow.document.write('<style>'+css+'</style>');
iframe.contentWindow.document.write(html);
iframe.contentWindow.document.close();
I have used a div with a fixed height, and the problem with auto is that it resizes the element, I fixed that with the following code after my inner HTML was set:
element.style.height = "auto";
element.style.height = "400px";
now scrollHeight is resetted correctly and gives the real height of the inner HTML
I had this same issue -- A content editable div whose scrollHeight wouldn't shrink when lines were removed.
The accepted answer didn't fix the problem for me, however, removing the div's parent's display: flex; did.
I need to resize an iframe to match its content, but the height properties I have tried don't account for elements with position: fixed.
Assume a document with only two elements with the absolute and fixed classes.
body { padding: 0; margin: 0; }
.absolute {
position: absolute;
height: 100px;
}
.fixed {
position: fixed;
height: 200px;
}
html.scrollHeight 0 (viewport height in Opera/Firefox)
html.offsetHeight 0
body.scrollHeight 0 (viewport height in Chrome)
body.offsetHeight 0
body.outerHeight 0
If I add html { position: relative; }, html.scrollHeight will be 100px in Chrome, but no value will be 200px. At first I also had an issue with floats, but I solved that by adding a clearfix to body.
I made a jsbin here: http://jsbin.com/ehixiq
If it's not possible to get the real height, what would be my best workaround? I only need to support the latest versions of Opera, Chrome and Firefox.
I've found the best way is to use javascript as it can get the height reliably after rendering. In a recent project I did this with jQuery to get full height of the window:
$(document).height()
You could do something like this for element heights:
$('.element2').height($('.element1').height())
Update:
$('iframe').height($('iframe').parent().height())
The only way I could figure out was to get the actual bottom position of all elements:
var els = Array.prototype.slice.call(document.body.getElementsByTagName('*'));
var elHeights = [];
for (var i = 0, l = els.length; i < l; i++) {
elHeights.push(els[i].scrollTop + els[i].offsetHeight);
}
var docHeight = Math.max.apply(Math, elHeights);
Browsers managed between 5-100k operations per second on a DOM with 100 elements, and in my case that's about the size most documents will have.
I have an external style sheet with this in it:
.box {
padding-left:30px;
background-color: #BBFF88;
border-width: 0;
overflow: hidden;
width: 400px;
height: 150px;
}
I then have this:
<div id="0" class="box" style="position: absolute; top: 20px; left: 20px;">
When I then try to access the width of the div:
alert(document.getElementById("0").style.width);
A blank alert box comes up.
How can I access the width property which is defined in my style sheet?
NOTE: The div displays with the correct width.
You should use window.getComputedStyle to get that value. I would recommend against using offsetWidth or clientWidth if you're looking for the CSS value because those return a width which includes padding and other calculations.
Using getComputedStyle, your code would be:
var e = document.getElementById('0');
var w = document.defaultView.getComputedStyle(e,null).getPropertyValue("width");
The documentation for this is given at MDC : window.getComputedStyle
offsetWidth displays the actual width of your div:
alert(document.getElementById("0").offsetWidth);
This width can be different to what you have set in your css, though.
The jQuery way would be (I really don't want to mention them all the time, but that's what all the libraries are there for):
$("#0").width(); // should return 400
$("#0").offsetWidth(); // should return 400 as well
$("#0").css("width"); // returns the string 400px
I hope this is helpful:
function changecss(theClass,element,value) {
//Last Updated on June 23, 2009
//documentation for this script at
//http://www.shawnolson.net/a/503/altering-css-class-attributes-with-javascript.html
var cssRules;
var added = false;
for (var S = 0; S < document.styleSheets.length; S++){
if (document.styleSheets[S]['rules']) {
cssRules = 'rules';
} else if (document.styleSheets[S]['cssRules']) {
cssRules = 'cssRules';
} else {
//no rules found... browser unknown
}
for (var R = 0; R < document.styleSheets[S][cssRules].length; R++) {
if (document.styleSheets[S][cssRules][R].selectorText == theClass) {
if(document.styleSheets[S][cssRules][R].style[element]){
document.styleSheets[S][cssRules][R].style[element] = value;
added=true;
break;
}
}
}
if(!added){
if(document.styleSheets[S].insertRule){
document.styleSheets[S].insertRule(theClass+' { '+element+': '+value+'; }',document.styleSheets[S][cssRules].length);
} else if (document.styleSheets[S].addRule) {
document.styleSheets[S].addRule(theClass,element+': '+value+';');
}
}
}
}
It is taken from here.
The answers are mostly correct, but will do your head in when you try to use them as they depend on the rendering mode of the browser (aka strict/quirks mode, browser vender, etc) - the last answer is the best... use jquery.