Develop Reference

how to update style properties in <style> tag using javascript [duplicate]

Is it possible to make changes to a CSS rule-set dynamically (i.e. some JS which would change a CSS rule-set when the user clicks a widget)
This particular CSS rule-set is applied to lots of elements (via a class selector) on the page and I want to modify it when the user clicks the widget, so that all the elements having the class change.

You can, but it's rather cumbersome. The best reference on how to do it is the following article: Totally Pwn CSS with Javascript (web archive link).
I managed to get it to work with Firefox and IE - I couldn't in Chrome, though it appears that it supports the DOM methods.ricosrealm reports that it works in Chrome, too.

This is a modern version based on Totally Pwn CSS with Javascript. It's ES6 I hope don't mind.
function getCSSRule(ruleName) {
ruleName = ruleName.toLowerCase();
var result = null;
var find = Array.prototype.find;
find.call(document.styleSheets, styleSheet => {
result = find.call(styleSheet.cssRules, cssRule => {
return cssRule instanceof CSSStyleRule
&& cssRule.selectorText.toLowerCase() == ruleName;
});
return result != null;
});
return result;
}
This function returns a CSSStyleRule that you can use like this:
var header = getCSSRule('#header');
header.style.backgroundColor = 'red';
Also document.styleSheets list references of the CSSStylesSheets Objects. Other way to acces a specific sytleSheet in the page is by assigning an id to the style or link element in the html code, and get it in javascript using document.getElementById('my-style').sheet. This are some useful methods:
Major Browsers and IE9+ : insertRule(), deleteRule(), removeProperty().
Major Browsers, Firefox? and IE9+ : setProperty().
<stye id="my-style" ...
....
var myStyle = document.getElementById('my-style').sheet
myStyle.insertRule('#header { background: red; }', 0);
It is also possible to dynamically create a new style element to store dynamic created styles, I think should be way to avoid conflicts.

You can edit CLASS in document styleshets as follows
[...document.styleSheets[0].cssRules].find(x=> x.selectorText=='.box')
.style.background= 'red';
function edit() {
[...document.styleSheets[0].cssRules].find(x=> x.selectorText=='.box')
.style.background= 'red';
}
.box {
margin: 10px;
padding: 10px;
background: yellow;
}
<button onclick="edit()" >Click me</button>
<div class="box" >My box 1</div>
<div class="box" >My box 2</div>
<div class="box" >My box 3</div>

I tried the code via link from #alex-gyoshev comment, but it dosn't work
it fails on the CSS rules with Google fonts in Chrome
it fails on FireFox security checks
So I changed it slightly, but deleted delete functionality since it wasn't needed for me. Checked in IE 11, FireFox 32, Chrome 37 and Opera 26.
function getCSSRule(ruleName) { // Return requested style object
ruleName = ruleName.toLowerCase(); // Convert test string to lower case.
var styleSheet;
var i, ii;
var cssRule = false; // Initialize cssRule.
var cssRules;
if (document.styleSheets) { // If browser can play with stylesheets
for (i = 0; i < document.styleSheets.length; i++) { // For each stylesheet
styleSheet = document.styleSheets[i];
if (!styleSheet.href) {
if (styleSheet.cssRules) { // Browser uses cssRules?
cssRules = styleSheet.cssRules; // Yes --Mozilla Style
} else { // Browser usses rules?
cssRules = styleSheet.rules; // Yes IE style.
} // End IE check.
if (cssRules) {
for (ii = 0; ii < cssRules.length; ii++) {
cssRule = cssRules[ii];
if (cssRule) { // If we found a rule...
// console.log(cssRule);
if (cssRule.selectorText) {
console.log(cssRule.selectorText);
if (cssRule.selectorText.toLowerCase() == ruleName) { // match ruleName?
return cssRule; // return the style object.
}
}
}
}
}
}
}
}
return false; // we found NOTHING!
}

Depending on what you're trying to achieve, a better solution might be to change/add a class to a containing element (body would do!), and define classes accordingly.
.yourclass { color: black }
#wrapper.foo .yourclass { color: red }
#wrapper.bar .yourclass { color: blue }
then you can just use
document.getElementById('wrapper').className='foo';
(or your chosen js framework's wrapper for the same) to change everything with class yourclass inside whatever your wrapper element is.

The APIs for editing stylesheets with JS are, sadly, not consistent across browsers. The YUI Stylesheet Utility attempts to smooth over these differences so you could just use that. You could also look at the source code to figure out how it works if you don't want to use YUI itself.

give your style tag an id, like <style id="ssID">
if someonelse is making your styles for you
tell THAT person to give the style tag an id -
that way you can access it directly without
scrambling around wondering what its index is
// create a hash table
var cssHash = {};
// loop through and populate the hash table
for (let i in (r = ss0.sheet.rules)) {
// selectorText is the name of the rule - set the value equal to the rule
cssHash[r[i].selectorText] = r[i];
}
now you have a hash table for everything in the style sheet -
note that some values will be undefined, but not for
any of the things you care about
if you have, for instance, a class called #menuItem
and you want to change its color to black, do this
cssHash['#menuItem'].style.color = #000;
that line will set the color of the style of the rule
whose index was looked up in the hash table (cssHash)
by the name '#menuItem'
more importantly, you probably have several different
classes that you want to change all at once
kind of like when you switched majors in college
let's say you have four different classes
and you want to set all of their background colors
to the same value, that some user selected from an input
the color selector tag is <input id="bColor" type="color">
and the class rules you want to change are called
#menuItem .homeAddr span and #vacuum:hover
// create a listener for that color selector
bColor.addEventListener('input', function (e) {
// loop through a split list of the four class names
'#menuItem .homeAddr span #vacuum:hover'.split(' ').forEach(function (obj) {
// use the hash table to look up the index of each name
// and set the background color equal to the color input's value
cssHash[obj].style.backgroundColor = bColor.value;
});
}, false); // false added here for the sake of non-brevity

While setAttribute is nice, there is a standard way of doing this across most browsers:
htmlElement.className = 'someClass';
To do it over many elements, you will need a cross browser solution:
function getElementsByClassName( className, context, tagName ) {
context = context || document;
if ( typeof context.getElementsByClassName === 'function' )
return context.getElementsByClassName( className );
if ( typeof context.getElementsByTagName !== 'function' )
return [];
var elements = typeof tagName === 'string' ? context.getElementsByTagName( tagName ) :
context.getElementsByTagName('*'),
ret = [];
for ( var i = 0, il = elements.length; i < il; i++ )
if ( elements[ i ].className.match( className ) )
ret.push( elements[ i ] );
return ret;
}
var elements = getElementsByClassName('someClass');
for ( var i = 0, il = elements.length; i < il; i++ )
elements[ i ].className = 'newClass';
You may want to replace the line:
if ( elements[ i ].className.match( className ) )
With some Regular Expression, but you will have to escape special characters in that case.

To check all stylesheets for the rule and set it:
Your rule:
.aaa: {
background-color: green
}
[...document.styleSheets].flatMap(s=>[...s.cssRules])
.find(i=>i.selectorText=='.aaa').style.backgroundColor = 'red';
Note that the css styles, when accessed through javascript, do not have dashes in them. In the example above, background-color becomes backgroundColor

javascript .style property of span tag in anchor tag not working as expected

I am trying to style some buttons for my website
This is my html
<div>
<a class="page_numbers"><span>100</span></a>
<a class="page_numbers"><span>2</a></span></div>
this is my css
.page_numbers{
display:table-cell;
border:solid;
padding:0px;
border-radius:100px;
width:50px;
height:50px;
text-align:center;
vertical-align:middle;
}
div {
display:table;
border-spacing:10px;
}
}
and finally this is my javascript
var obj=document.getElementsByClassName("page_numbers")
for (i in obj){
console.log(obj[i].children)
obj[i].children[0].style.color="black"
obj[i].style.borderColor="rgb(85,170,255)"
function jun(i){
obj[i].addEventListener('mouseenter',function(){obj[i].style.background="yellow";obj[i].style.color="red"},true)
//
obj[i].addEventListener('mouseleave',function(){
obj[i].style.background="white";
obj[i].style.color="rgb(12,31,22)";},true)
}
jun(i);
}
the background color changes on mouseleave and enter but not the font color...I suppose I am doing something wrong along the way or I am missing a fundamental concept
this is my jsfiddle link
http://jsfiddle.net/repzeroworld/boqv8hak/
advice please..still learning JS

Firstly, all of this should be in CSS and is trivial to do so
.page_numbers:hover
{
background-color: yellow;
}
.page_numbers:hover span
{
color: red;
}
Now the issue you are having is that on about the 4th line of your JS you explicitly set the color of the child element (the span) inside the .page_number element to be black. Now on you mouse enter you are setting the color on the page_number element, but since the child has a style applied directly to it (i.e. color: black) it does not inherit the parent style. Inline styles (i.e. style applied directly to the element with the style="" attribute, which is what JS does) always have the highest precedence. This is why it is generally not best practice to put inline styles on an element, as you have just seen, they are pretty much impossible to override. So change either the child to not have an explicit style, or on the mouse enter change the child not the parent
var obj = document.getElementsByClassName("page_numbers")
for (i in obj) {
console.log(obj[i].children)
obj[i].children[0].style.color = "black"
obj[i].style.borderColor = "rgb(85,170,255)"
function jun(i) {
obj[i].addEventListener('mouseenter', function () {
obj[i].style.background = "yellow";
obj[i].children[0].style.color = "red"
}, true)
//
obj[i].addEventListener('mouseleave', function () {
obj[i].style.background = "white";
obj[i].children[0].style.color = "rgb(12,31,22)";
}, true)
}
jun(i);
}
or
var obj = document.getElementsByClassName("page_numbers")
for (i in obj) {
console.log(obj[i].children)
obj[i].style.borderColor = "rgb(85,170,255)"
function jun(i) {
obj[i].addEventListener('mouseenter', function () {
obj[i].style.background = "yellow";
obj[i].style.color = "red"
}, true)
//
obj[i].addEventListener('mouseleave', function () {
obj[i].style.background = "white";
obj[i].style.color = "rgb(12,31,22)";
}, true)
}
jun(i);
}
but as I indicated all this should really be in CSS

You trying to change color of a instead of span
Try like this
obj[i].children[0].style.color = "red"
JSFIDDLE

changing CSS class definition

Suppose I have this class:
.MyClass{background:red;}
This class applies to several divs. I want to change the color of the background to orange by changing the color defined in MyClass.
Now, I know I could do $('.MyDiv').css('background', 'orange');
But my question is really this: how do I change the CSS class definition so that MyClass elements now have background:orange;? I want to be able to change several CSS color properties from one color to another.
Thanks.

Actually altering your stylesheet is pretty challenging. Much more easily, though, you can switch out your stylesheet for a different one, which may be sufficient for your purposes. See How do I switch my CSS stylesheet using jQuery?.
For actually altering the stylesheet content, How to change/remove CSS classes definitions at runtime? will get you started.

It is difficult to find the rule you want because you have to iterate through the document.styleSheets[i].cssRules array. (and compare your class name with the selectorText attribute)
So my solution to this problem is to add a new CSS class, remove the old CSS class from the HTML element and add this class instead of it.
var length = getCssRuleLength();
var newClassName = "css-class-name" + length;
//remove preview css class from html element.
$("#your-html-element").removeClass("css-class-name");
$("#your-html-element").removeClass("css-class-name" + (length-1));
$("#your-html-element").addClass(newClassName);
//insert a css class
insertCssRule("." + newClassName + ' { max-width: 100px; }', length);
function getCssRuleLength() {
var length = 0;
if (document.styleSheets[1].cssRules) {
length = document.styleSheets[1].cssRules.length;
} else if (document.styleSheets[1].rules) { //ie
length = document.styleSheets[1].rules.length;
}
return length;
}
function insertCssRule(rule, index) {
if (document.styleSheets[1].cssRules) {
document.styleSheets[1].insertRule(rule, index);
} else if (document.styleSheets[1].rules) { //ie
document.styleSheets[1].addRule(rule, index);
}
}

Here's my answer in case anyone stumbles upon this. Give your elements a new class name that doesn't already exist, then dynamically add a style segment:
var companyColor = 'orange' //define/fetch the varying color here
var style = '<style>.company-background {background-color: ' + companyColor + '; color: white;}</style>';
$('html > head').append($(style));
//give any element that needs this background color the class "company-background"

You have 2 options
add a new stylesheet that overrides this .MyClass
have a second class with the different property, and change the class Name on these elements

Looking at your question, I think a better approach is to switch MyClass with something else using JavaScript rather than to change the properties of the class dynamically.
But if you are still keen you can switch CSS stylesheets with jQuery http://www.cssnewbie.com/simple-jquery-stylesheet-switcher/

var changeClassProperty = function(sheetName, className, propertyName, newValue, includeDescendents) {
var ending = '$';
setValue = '';
if (includeDescendents === true) {
ending = '';
}
if (typeof(newValue) != 'undefined') {
setValue = newValue;
}
var list = document.styleSheets;
for (var i = 0, len = list.length; i < len; i++) {
var element = list[i];
if (element['href'] && element['href'].match(new RegExp('jquery\.qtip'))) {
var cssRules = element.cssRules;
for (j = 0, len2 = cssRules.length; j < len2; j++) {
var rule = cssRules[j];
if (rule.selectorText.match(new RegExp(className + ending))) {
cssRules[j].style.backgroundColor = setValue;
console.log(cssRules[j].style.backgroundColor);
}
}
}
}
}
changeClassProperty('jquery.qtip', 'tipsy', 'backgroundColor', 'yellow');

You'd be much better off adding and removing classes instead of attempting to change them.
For example
.red {
background: red;
}
.orange {
background: orange;
}
$('#div').click(function(){
$(this).removeClass('red').addClass('orange');
});

Is there any way to reset :after/:before CSS rules for an element?

Is there any way to (robustly) reset any possible :after and :before CSS rules for a newly created element?
Usually you can just set the style rules you want to reset on the element directly (with !important if you want to be sure), but I don't know of any way of changing rules defined in :after on the element only.
(Only has to work with Chrome, if at all possible.)
An example at jsFiddle.
The content added with the :before/:after rules is affecting the value returned by clientHeight.

There is a DOM2 API for that matter. The correct way to do this is
document.getOverrideStyle(p, ':after').display = 'none'; // or
document.getOverrideStyle(p, ':after').cssText = 'display: none !important;';
Unfortunately, no browser has implemented it. (Webkit returns null, Firefox has no such method). It looks like CSS3 doesn't even bother talking about that anymore, maybe because the usecases are very rare.
So you're gonna have to do some id/className magic as suggested above or in the other thread

I'd just assign a class name to the new elements that does not have :before / :after content.
Example - http://jsfiddle.net/84kZK/1/

Ah, okay. You can write new CSS that resets the offending :before/:after pseudo-elements:
function resetPsuedo(el) {
if (!el.id) el.id = makeId();
var selector = "#" + el.id;
var head = document.getElementsByTagName('head')[0],
style = document.createElement('style'),
rules = document.createTextNode(selector + ":before, " + selector + ":after { content: '' }");
style.type = 'text/css';
if(style.styleSheet)
style.styleSheet.cssText = rules.nodeValue;
else style.appendChild(rules);
head.appendChild(style);
}
function makeId() {
var text = "";
var possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
for (var i=0; i < 15; i++)
text += possible.charAt(Math.floor(Math.random() * possible.length));
return text;
}
​Assigning a random ID to the element you pass in (if it doesn't have one) allows you to hack-up inline styles—rather than accessing el.beforeStyle, you can use CSS selectors: el#rkhjr828t9g:before.
You may need to add more rules to fully reset the styles. jsFiddle: view me!
http://www.w3.org/TR/CSS21/generate.html#before-after-content
​The :before and :after pseudo-elements interact with other boxes as
if they were real elements inserted just inside their associated
element.
For example, the following document fragment and style sheet:
<p> Text </p> p:before { display: block; content: 'Some'; }
...would render in exactly the same way as the following document
fragment and style sheet:
<p><span>Some</span> Text </p> span { display: block }
Similarly, the following document fragment and style sheet:
<h2> Header </h2> h2:after { display: block; content: 'Thing'; }
...would render in exactly the same way as the following document
fragment and style sheet:
<h2> Header <span>Thing</span></h2> h2 { display: block; }
span { display: block; }

Use ruleSelector("ref::before")[0].style instead of document.getOverrideStyle(ref, ':before').
http://jsfiddle.net/s3fv8e5v/4/
<!DOCTYPE html>
<title>CSS</title>
<style>
body {
font: 200%/1.45 charter;
}
ref::before {
content: '\00A7';
letter-spacing: .1em;
}
</style>
<article>The seller can, under Business Law <ref>1782</ref>, offer a full refund to buyers. </article>
<script>
function ruleSelector(selector) {
function uni(selector) {
return selector.replace(/::/g, ':') // for Firefox
}
return Array.prototype.filter.call(Array.prototype.concat.apply([], Array.prototype.map.call(document.styleSheets, function(x) {
return Array.prototype.slice.call(x.cssRules);
})), function(x) {
return uni(x.selectorText) === uni(selector);
});
}
var toggle = false,
pseudo = ruleSelector("ref::before").slice(-1);
document.querySelector("article").onclick = function() {
pseudo.forEach(function(rule) {
if (toggle = !toggle)
rule.style.color = "red";
else
rule.style.color = "black";
});
}
</script>

How do I remove :hover?

I have a small problem with a script.
I want to have a default action on :hover for clients with Javascript disabled, but for those with Javascript enabled I want another action (actually... same action, but I want to add a small transition effect).
So... How can I do this? I am using jQuery.

Apply two classes to the relvant element. one contains the hover behaviour, and one contains all the other styling.
You can then use the jquery
$(element).removeClass('hover');
method to remove the class with the hover behaviour and then apply whatever you want using
$(element).bind('mouseover', function () { doSomething(); });
$(element).bind('mouseout', function () { doSomething(); });

How about putting the :hover fall-back in a stylesheet that is only loaded if javascript is disabled?
<noscript>
<link href="noscript.css" rel="stylesheet" type="text/css" />
</noscript>

Here is a solution without hack classes:
CSS:
a {color: blue;}
a:hover {color: red;}
jQuery (uses jQueryUI to animate color):
$('a').hover(
function() {
$(this)
.css('color','blue')
.animate({'color': 'red'}, 400);
},
function() {
$(this)
.animate({'color': 'blue'}, 400);
}
);
demo

I think the best approach would be to leave the :hover behavior as a fall-back for non-javascript users and then use JQuery to create mouseover and mouseout event handlers to create a different effect for javascript-enabled users.
JQuery Javascript Library - Events/mouseover

It's a very old question but I feel the urge to tell that modernizr provides a very good way to implement these kind of fallbacks.
Just include modernizr in the head and you can do these:
.no-js a:hover {
set background color and stuff like that
for cases when no javascript is present
}
On the other hand if you want to do this the other way and only set css when js is present
.js a:hover {
set background color to default
and the text decoration
}
It is more or less the same solution as adding a hover tag to the markup, but a little more robust.

I HAVE FOUND YOUR SOLUTION
basically you start out by redefining what you did with the css hover.
(naturally you would do this by dynamically pulling the information from the style)
then do whatever you want to in jquery with mouseover/mouseout events
this allows you to keep the :hover event in your css because jquery is binding your original styles to the element. In essence disabling the :hover event.
if your css is:
a.class {
background-color: #000000;
background-position: 0 0;
}
a.class:hover {
background-color: #ffffff;
background-position: 100% -50px;
}
your jquery would be somthing like:
jQuery("a.class").each(function () {
var oldBackgroundColor = jQuery(this).css("backgroundColor");
var oldBackgroundPosition = jQuery(this).css("backgroundPosition");
jQuery(".class").css({
'backgroundColor':oldBackgroundColor,
'backgroundPosition':oldBackgroundPosition
});
})
.bind("mouseover", function() {
doSomething();
})
.bind("mouseout", function() {
doSomething();
})

You can redraw element after click
function redraw(element) {
if (!element) { return; }
let n = document.createTextNode(' ');
let disp = element.style.display; // don't worry about previous display style
element.appendChild(n);
element.style.display = 'none';
setTimeout(function(){
element.style.display = disp;
n.parentNode.removeChild(n);
}, 100); // you can play with this timeout to make it as short as possible
}

You can globally enable behavior across the entire document by using a single css rule, and then disable that rule in one statement in javascript, while installing the new event handler.
Add a class to your html body tag:
<html>
<body class="use-hover">
...
Default behavior in your css, let's say to bold links on hover:
body.use-hover a:hover
font-weight: bold
And in your js, when run will remove the default behavior and do something else:
$(function() {
$('body').removeClass('use-hover');
$('a').live('mouseover', function() {
// Do something when hovered
}).live('mouseout', function() {
// Do something after hover is lost
});
});

You could strip all :hover style rules from document.styleSheets.
Just go through all CSS styles with JavaScript and remove all rules, which contain ":hover" in their selector. I use this method when I need to remove :hover styles from bootstrap 2.
_.each(document.styleSheets, function (sheet) {
var rulesToLoose = [];
_.each(sheet.cssRules, function (rule, index) {
if (rule.selectorText && rule.selectorText.indexOf(':hover') > 0) {
rulesToLoose.push(index);
}
});
_.each(rulesToLoose.reverse(), function (index) {
if (sheet.deleteRule) {
sheet.deleteRule(index);
} else if (sheet.removeRule) {
sheet.removeRule(index);
}
});
});
I did use underscore for iterating arrays, but one could write those with pure js loop as well:
for (var i = 0; i < document.styleSheets.length; i++) {}

Vanilla JS version of Mikael Lepistö's answer
for (var i = 0; i < document.styleSheets.length; i++) {
var sheet = document.styleSheets[i];
var rulesToLose = [];
for (var j = 0; j < sheet.cssRules.length; j++) {
var rule = sheet.cssRules[j];
if (rule && rule.selectorText && rule.selectorText.indexOf(':hover') >= 0) {
rulesToLose.push(j);
}
}
// Iterate backwards to prevent pointing to the wrong index while sheet rules get deleted
for (var k = rulesToLose.length - 1; k >= 0; k--) {
sheet.deleteRule(rulesToLose[k]);
}
}