400

I need to create a CSS stylesheet class dynamically in JavaScript and assign it to some HTML elements like - div, table, span, tr, etc and to some controls like asp:Textbox, Dropdownlist and datalist.

Is it possible?

It would be nice with a sample.

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3
  • 2
    take a look at github.com/Box9/jss Commented Sep 7, 2012 at 14:49
  • See also stackoverflow.com/questions/1212500/… Commented Sep 7, 2012 at 15:39
  • Notice in some cases what you really want might not be exactly creating a css class and applying it, but you've come here because you want to add multiple styles at once maybe because it's "faster"(easier to type). In that case, check the answers on this question, some of them are very useful: stackoverflow.com/questions/3968593/… Commented Jun 29, 2021 at 3:30

18 Answers 18

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525

Here is an option:

var style = document.createElement('style');
style.type = 'text/css';
style.innerHTML = '.cssClass { color: #f00; }';
document.getElementsByTagName('head')[0].appendChild(style);

document.getElementById('someElementId').className = 'cssClass';
<div id="someElementId">test text</div>

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18 Comments

My use case is a bookmarklet that is highlighting certain elements for QA purposes.
Pretty sure this results in a unknown runtime error in IE 8 and less.
Another use case would be where you want a single JS lib without dependencies on CSS files. In my case I want lightweight growl-style alert popups out-of-the-box.
I once needed to highlight and unhighlight many elements in a page at once, corresponding to a user's selection. Applying and removing the classes to all the elements was slooooow. So instead, in the browser after my ajax request returned data, I created one css class per possible selection and applied it to each element, defining the rule for all classes with no attributes. Once a selection was made, rewriting the rule itself resulted in amazing lightning speed updating all the elements on the page. So yeah, there's a use case.
I know this is an old post, but to update it, document.getElementsByTagName('head')[0].appendChild(style); should be document.head.appendChild(style).
|
133

Found a better solution, which works across all browsers.
Uses document.styleSheet to add or replace rules. Accepted answer is short and handy but this works across IE8 and less too.

function createCSSSelector (selector, style) {
  if (!document.styleSheets) return;
  if (document.getElementsByTagName('head').length == 0) return;

  var styleSheet,mediaType;

  if (document.styleSheets.length > 0) {
    for (var i = 0, l = document.styleSheets.length; i < l; i++) {
      if (document.styleSheets[i].disabled) 
        continue;
      var media = document.styleSheets[i].media;
      mediaType = typeof media;

      if (mediaType === 'string') {
        if (media === '' || (media.indexOf('screen') !== -1)) {
          styleSheet = document.styleSheets[i];
        }
      }
      else if (mediaType=='object') {
        if (media.mediaText === '' || (media.mediaText.indexOf('screen') !== -1)) {
          styleSheet = document.styleSheets[i];
        }
      }

      if (typeof styleSheet !== 'undefined') 
        break;
    }
  }

  if (typeof styleSheet === 'undefined') {
    var styleSheetElement = document.createElement('style');
    styleSheetElement.type = 'text/css';
    document.getElementsByTagName('head')[0].appendChild(styleSheetElement);

    for (i = 0; i < document.styleSheets.length; i++) {
      if (document.styleSheets[i].disabled) {
        continue;
      }
      styleSheet = document.styleSheets[i];
    }

    mediaType = typeof styleSheet.media;
  }

  if (mediaType === 'string') {
    for (var i = 0, l = styleSheet.rules.length; i < l; i++) {
      if(styleSheet.rules[i].selectorText && styleSheet.rules[i].selectorText.toLowerCase()==selector.toLowerCase()) {
        styleSheet.rules[i].style.cssText = style;
        return;
      }
    }
    styleSheet.addRule(selector,style);
  }
  else if (mediaType === 'object') {
    var styleSheetLength = (styleSheet.cssRules) ? styleSheet.cssRules.length : 0;
    for (var i = 0; i < styleSheetLength; i++) {
      if (styleSheet.cssRules[i].selectorText && styleSheet.cssRules[i].selectorText.toLowerCase() == selector.toLowerCase()) {
        styleSheet.cssRules[i].style.cssText = style;
        return;
      }
    }
    styleSheet.insertRule(selector + '{' + style + '}', styleSheetLength);
  }
}

Function is used as follows.

createCSSSelector('.mycssclass', 'display:none');
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13 Comments

Confirmed working with IE8. I did have to add a "styleSheet.cssRules[i].selectorText &&" and "styleSheet.rules[i].selectorText &&"in the mediaType for-loop ifs because it didn't work in Chrome, apparently sometimes the selectorText isn't defined.
@w00t Could you please paste or edit the code to make it work?
I just opened the Chrome (Version 34.0.1847.132) pasted the functions and executed it, but it didn't work: "TypeError: Cannot read property 'length' of null". Can it be that does not work creating it from developer console?
@dnuske I encountered the same issue. it turns out that styleSheet.cssRules evaluates to null. the fix I've used is to create a new variable var styleSheetLength = styleSheet.cssRules ? styleSheet.cssRules.length : 0 and substitute its usage over the implementation of the function.
I used the accepted answer before, but because I want to modify the style sheet, using the code on this link: //stackoverflow.com/questions/50036922/… , it didn't work with accepted answer, but worx with your's thank you very much :-)
|
33

Short answer, this is compatible "on all browsers" (specifically, IE8/7):

function createClass(name,rules){
    var style = document.createElement('style');
    style.type = 'text/css';
    document.getElementsByTagName('head')[0].appendChild(style);
    if(!(style.sheet||{}).insertRule) 
        (style.styleSheet || style.sheet).addRule(name, rules);
    else
        style.sheet.insertRule(name+"{"+rules+"}",0);
}
createClass('.whatever',"background-color: green;");

And this final bit applies the class to an element:

function applyClass(name,element,doRemove){
    if(typeof element.valueOf() == "string"){
        element = document.getElementById(element);
    }
    if(!element) return;
    if(doRemove){
        element.className = element.className.replace(new RegExp("\\b" + name + "\\b","g"));
    }else{      
        element.className = element.className + " " + name;
    }
}

Here's a little test page as well: https://gist.github.com/shadybones/9816763

The key little bit is the fact that style elements have a "styleSheet"/"sheet" property which you can use to to add/remove rules on.

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4 Comments

so this creates a new "style" element every class creation? So if I were to create 1000+ classes in a for loop based on data, this would need to apply document.head.appendChild 1000 times?
for me in chrome style.sheet and style.styleSheet doesn't exist
it does not work in Chrome anymore at least in January 2022
If you create a class referenced by ID such as #myItem{color:red} you don't even need to call applyClass, the browser automatically adds it to the CSS stylesheets rules.
19

There is a light jQuery plugin which allows to generate CSS declarations: jQuery-injectCSS

In fact, it uses JSS (CSS described by JSON), but it's quite easy to handle in order to generate dynamic css stylesheets.

$.injectCSS({
    "#test": {
        height: 123
    }
});
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1 Comment

similar to stackoverflow.com/questions/1212500/… .
10

One liner, attach one or many new cascading rule(s) to the document.

This example attach a cursor:pointer to every button, input, select.

document.body.appendChild(Object.assign(document.createElement("style"), {textContent: "select, button, input {cursor:pointer}"}))
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Comments

8

Contrary to other answers official/clean way to add CSS dynamically would be via document.adoptedStyleSheets.

See example from MDN (comments stripped):

const sheet = new CSSStyleSheet();
sheet.replaceSync("a { color: red; }");
document.adoptedStyleSheets = [sheet];

It is supported by all modern browsers, not sure about old IE though.

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1 Comment

Yes, this is the actual answer for all modern browsers. Thanks.
7

YUI has by far the best stylesheet utility I have seen out there. I encourage you to check it out, but here's a taste:

// style element or locally sourced link element
var sheet = YAHOO.util.StyleSheet(YAHOO.util.Selector.query('style',null,true));

sheet = YAHOO.util.StyleSheet(YAHOO.util.Dom.get('local'));


// OR the id of a style element or locally sourced link element
sheet = YAHOO.util.StyleSheet('local');


// OR string of css text
var css = ".moduleX .alert { background: #fcc; font-weight: bold; } " +
          ".moduleX .warn  { background: #eec; } " +
          ".hide_messages .moduleX .alert, " +
          ".hide_messages .moduleX .warn { display: none; }";

sheet = new YAHOO.util.StyleSheet(css);

There are obviously other much simpler ways of changing styles on the fly such as those suggested here. If they make sense for your problem, they might be best, but there are definitely reasons why modifying CSS is a better solution. The most obvious case is when you need to modify a large number of elements. The other major case is if you need your style changes to involve the cascade. Using the DOM to modify an element will always have a higher priority. It's the sledgehammer approach and is equivalent to using the style attribute directly on the HTML element. That is not always the desired effect.

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Comments

6

Here is Vishwanath's solution slightly rewritten with comments :

function setStyle(cssRules, aSelector, aStyle){
    for(var i = 0; i < cssRules.length; i++) {
        if(cssRules[i].selectorText && cssRules[i].selectorText.toLowerCase() == aSelector.toLowerCase()) {
            cssRules[i].style.cssText = aStyle;
            return true;
        }
    }
    return false;
}

function createCSSSelector(selector, style) {
    var doc = document;
    var allSS = doc.styleSheets;
    if(!allSS) return;

    var headElts = doc.getElementsByTagName("head");
    if(!headElts.length) return;

    var styleSheet, media, iSS = allSS.length; // scope is global in a function
    /* 1. search for media == "screen" */
    while(iSS){ --iSS;
        if(allSS[iSS].disabled) continue; /* dont take into account the disabled stylesheets */
        media = allSS[iSS].media;
        if(typeof media == "object")
            media = media.mediaText;
        if(media == "" || media=='all' || media.indexOf("screen") != -1){
            styleSheet = allSS[iSS];
            iSS = -1;   // indication that media=="screen" was found (if not, then iSS==0)
            break;
        }
    }

    /* 2. if not found, create one */
    if(iSS != -1) {
        var styleSheetElement = doc.createElement("style");
        styleSheetElement.type = "text/css";
        headElts[0].appendChild(styleSheetElement);
        styleSheet = doc.styleSheets[allSS.length]; /* take the new stylesheet to add the selector and the style */
    }

    /* 3. add the selector and style */
    switch (typeof styleSheet.media) {
    case "string":
        if(!setStyle(styleSheet.rules, selector, style));
            styleSheet.addRule(selector, style);
        break;
    case "object":
        if(!setStyle(styleSheet.cssRules, selector, style));
            styleSheet.insertRule(selector + "{" + style + "}", styleSheet.cssRules.length);
        break;
    }
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5

As of IE 9. You can now load a text file and set a style.innerHTML property. So essentially you can now load a css file through ajax (and get the callback) and then just set the text inside of a style tag like this.

This works in other browsers, not sure how far back. But as long as you don't need to support IE8 then it would work.

// RESULT: doesn't work in IE8 and below. Works in IE9 and other browsers.
$(document).ready(function() {
    // we want to load the css as a text file and append it with a style.
    $.ajax({
        url:'myCss.css',
        success: function(result) {
            var s = document.createElement('style');
            s.setAttribute('type', 'text/css');
            s.innerHTML = result;
            document.getElementsByTagName("head")[0].appendChild(s);
        },
        fail: function() {
            alert('fail');
        }
    })
});

and then you can have it pull an external file like the myCss.css

.myClass { background:#F00; }
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Comments

5

https://jsfiddle.net/xk6Ut/256/

One option to dynamically create and update CSS class in JavaScript:

  • Using Style Element to create a CSS section
  • Using an ID for the style element so that we can update the CSS
    class

.....

function writeStyles(styleName, cssText) {
    var styleElement = document.getElementById(styleName);
    if (styleElement) 
             document.getElementsByTagName('head')[0].removeChild(
        styleElement);
    styleElement = document.createElement('style');
    styleElement.type = 'text/css';
    styleElement.id = styleName;
    styleElement.innerHTML = cssText;
    document.getElementsByTagName('head')[0].appendChild(styleElement);
}

... 

    var cssText = '.testDIV{ height:' + height + 'px !important; }';
    writeStyles('styles_js', cssText)
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Comments

4

Using google closure:

you can just use the ccsom module:

goog.require('goog.cssom');
var css_node = goog.cssom.addCssText('.cssClass { color: #F00; }');

The javascript code attempts to be cross browser when putting the css node into the document head.

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Comments

4

An interesting project which could help you out in your task is JSS.

JSS is an authoring tool for CSS which allows you to use JavaScript to describe styles in a declarative, conflict-free and reusable way. It can compile in the browser, server-side or at build time in Node.

JSS library allows you to inject in the DOM/head section using the .attach() function.

Repl online version for evaluation.

Further information on JSS.

An example:

// Use plugins.
jss.use(camelCase())

// Create your style.
const style = {
  myButton: {
    color: 'green'
  }
}

// Compile styles, apply plugins.
const sheet = jss.createStyleSheet(style)

// If you want to render on the client, insert it into DOM.
sheet.attach()
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3

I was looking through some of the answers here, and I couldn't find anything that automatically adds a new stylesheet if there are none, and if not simply modifies an existing one that already contains the style needed, so I made a new function (should work accross all browsers, though not tested, uses addRule and besides that only basic native JavaScript, let me know if it works):

function myCSS(data) {
    var head = document.head || document.getElementsByTagName("head")[0];
    if(head) {
        if(data && data.constructor == Object) {
            for(var k in data) {
                var selector = k;
                var rules = data[k];

                var allSheets = document.styleSheets;
                var cur = null;

                var indexOfPossibleRule = null,
                    indexOfSheet = null;
                for(var i = 0; i < allSheets.length; i++) {
                    indexOfPossibleRule = findIndexOfObjPropInArray("selectorText",selector,allSheets[i].cssRules);
                    if(indexOfPossibleRule != null) {
                        indexOfSheet = i;
                        break;
                    }
                }

                var ruleToEdit = null;
                if(indexOfSheet != null) {

                    ruleToEdit = allSheets[indexOfSheet].cssRules[indexOfPossibleRule];

                } else {
                    cur = document.createElement("style");
                    cur.type =  "text/css";
                    head.appendChild(cur);
                    cur.sheet.addRule(selector,"");
                    ruleToEdit = cur.sheet.cssRules[0];
                    console.log("NOPE, but here's a new one:", cur);
                }
                applyCustomCSSruleListToExistingCSSruleList(rules, ruleToEdit, (err) => {
                    if(err) {
                        console.log(err);
                    } else {
                        console.log("successfully added ", rules, " to ", ruleToEdit);
                    }
                });
            }
        } else {
            console.log("provide one paramter as an object containing the cssStyles, like: {\"#myID\":{position:\"absolute\"}, \".myClass\":{background:\"red\"}}, etc...");
        }
    } else {
        console.log("run this after the page loads");
    }

};

then just add these 2 helper functions either inside the above function, or anywhere else:

function applyCustomCSSruleListToExistingCSSruleList(customRuleList, existingRuleList, cb) {
    var err = null;
    console.log("trying to apply ", customRuleList, " to ", existingRuleList);
    if(customRuleList && customRuleList.constructor == Object && existingRuleList && existingRuleList.constructor == CSSStyleRule) {
        for(var k in customRuleList) {
            existingRuleList["style"][k] = customRuleList[k];
        }

    } else {
        err = ("provide first argument as an object containing the selectors for the keys, and the second argument is the CSSRuleList to modify");
    }
    if(cb) {
        cb(err);
    }
}

function findIndexOfObjPropInArray(objPropKey, objPropValue, arr) {
    var index = null;
    for(var i = 0; i < arr.length; i++) {
        if(arr[i][objPropKey] == objPropValue) {
            index = i;
            break;
        }
    }
    return index;
}

(notice that in both of them I use a for loop instead of .filter, since the CSS style / rule list classes only have a length property, and no .filter method.)

Then to call it:

myCSS({
    "#coby": {
        position:"absolute",
        color:"blue"
    },
    ".myError": {
        padding:"4px",
        background:"salmon"
    }
})

Let me know if it works for your browser or gives an error.

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1 Comment

For some reason adding !important makes the declaration empty. Any idea how to use "important"?
2

Here is my modular solution: 

var final_style = document.createElement('style');
final_style.type = 'text/css';

function addNewStyle(selector, style){
  final_style.innerHTML += selector + '{ ' + style + ' } \n';
};

function submitNewStyle(){
  document.getElementsByTagName('head')[0].appendChild(final_style);

  final_style = document.createElement('style');
  final_style.type = 'text/css';
};

function submitNewStyleWithMedia(mediaSelector){
  final_style.innerHTML = '@media(' + mediaSelector + '){\n' + final_style.innerHTML + '\n};';
    submitNewStyle();
};

You basically anywhere in your code do:
addNewStyle('body', 'color: ' + color1); , where color1 is defined variable.

When you want to "post" the current CSS file you simply do submitNewStyle(),
and then you can still add more CSS later.

If you want to add it with "media queries", you have the option.
After "addingNewStyles" you simply use submitNewStyleWithMedia('min-width: 1280px');.

It was pretty useful for my use-case, as I was changing CSS of public (not mine) website according to current time. I submit one CSS file before using "active" scripts, and the rest afterwards (makes the site look kinda-like it should before accessing elements through querySelector).

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1 Comment

I’m gonna try this out today. Will let you know how this works in my use case. Fingers crossed!!!!
1

Looked through the answers and the most obvious and straight forward is missing: use document.write() to write out a chunk of CSS you need.

Here is an example (view it on codepen: http://codepen.io/ssh33/pen/zGjWga): 

<style>
   @import url(http://fonts.googleapis.com/css?family=Open+Sans:800);
   .d, body{ font: 3vw 'Open Sans'; padding-top: 1em; }
   .d {
       text-align: center; background: #aaf;
       margin: auto; color: #fff; overflow: hidden; 
       width: 12em; height: 5em;
   }
</style>

<script>
   function w(s){document.write(s)}
   w("<style>.long-shadow { text-shadow: ");
   for(var i=0; i<449; i++) {
      if(i!= 0) w(","); w(i+"px "+i+"px #444");
   }
   w(";}</style>");
</script> 

<div class="d">
    <div class="long-shadow">Long Shadow<br> Short Code</div>
</div>
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1 Comment

This is fine unless you need to create CSS rules after page load or are using XHTML.
1

For the benefit of searchers; if you are using jQuery, you can do the following:

var currentOverride = $('#customoverridestyles');

if (currentOverride) {
 currentOverride.remove();
}

$('body').append("<style id=\"customoverridestyles\">body{background-color:pink;}</style>");

Obviously you can change the inner css to whatever you want.

Appreciate some people prefer pure JavaScript, but it works and has been pretty robust for writing/overwriting styles dynamically.

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Comments

1 
function createCSSClass(selector, style, hoverstyle) 
{
    if (!document.styleSheets) 
    {
        return;
    }

    if (document.getElementsByTagName("head").length == 0) 
    {

        return;
    }
    var stylesheet;
    var mediaType;
    if (document.styleSheets.length > 0) 
    {
        for (i = 0; i < document.styleSheets.length; i++) 
        {
            if (document.styleSheets[i].disabled) 
            {
                continue;
            }
            var media = document.styleSheets[i].media;
            mediaType = typeof media;

            if (mediaType == "string") 
            {
                if (media == "" || (media.indexOf("screen") != -1)) 
                {
                    styleSheet = document.styleSheets[i];
                }
            } 
            else if (mediaType == "object") 
            {
                if (media.mediaText == "" || (media.mediaText.indexOf("screen") != -1)) 
                {
                    styleSheet = document.styleSheets[i];
                }
            }

            if (typeof styleSheet != "undefined") 
            {
                break;
            }
        }
    }

    if (typeof styleSheet == "undefined") {
        var styleSheetElement = document.createElement("style");
        styleSheetElement.type = "text/css";
        document.getElementsByTagName("head")[0].appendChild(styleSheetElement);
        for (i = 0; i < document.styleSheets.length; i++) {
            if (document.styleSheets[i].disabled) {
                continue;
            }
            styleSheet = document.styleSheets[i];
        }

        var media = styleSheet.media;
        mediaType = typeof media;
    }

    if (mediaType == "string") {
        for (i = 0; i < styleSheet.rules.length; i++) 
        {
            if (styleSheet.rules[i].selectorText.toLowerCase() == selector.toLowerCase()) 
            {
                styleSheet.rules[i].style.cssText = style;
                return;
            }
        }

        styleSheet.addRule(selector, style);
    }
    else if (mediaType == "object") 
    {
        for (i = 0; i < styleSheet.cssRules.length; i++) 
        {
            if (styleSheet.cssRules[i].selectorText.toLowerCase() == selector.toLowerCase()) 
            {
                styleSheet.cssRules[i].style.cssText = style;
                return;
            }
        }

        if (hoverstyle != null) 
        {
            styleSheet.insertRule(selector + "{" + style + "}", 0);
            styleSheet.insertRule(selector + ":hover{" + hoverstyle + "}", 1);
        }
        else 
        {
            styleSheet.insertRule(selector + "{" + style + "}", 0);
        }
    }
}





createCSSClass(".modalPopup  .header",
                                 " background-color: " + lightest + ";" +
                                  "height: 10%;" +
                                  "color: White;" +
                                  "line-height: 30px;" +
                                  "text-align: center;" +
                                  " width: 100%;" +
                                  "font-weight: bold; ", null);
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1 Comment

what if theres no current stylesheet on the document
0

This is what worked for me in Angular: In HTML I have button with programmatically created CSS with specific ID:

    <button [id]="'hoverbutton1'+item.key" [ngClass]="getHoverButtonClass()">
        <mat-icon class="icon">open_in_new</mat-icon>
    </button>

In typescript I created CSS and assign it to specific element with given ID:

addClasses(){
  var style1 = document.createElement('style');
  style1.innerHTML = '.hoverbutton'+this.item.key+' { display: none; }';
  document.getElementsByTagName('head')[0].appendChild(style1);
}

getHoverButtonClass() {
  return "hoverbutton"+this.item.key
}

This way I can create as many CSS classes as I want and assign them to elements individually. :)

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