Is it possible to import css stylesheets into a html page using Javascript? If so, how can it be done?
P.S the javascript will be hosted on my site, but I want users to be able to put in the <head> tag of their website, and it should be able to import a css file hosted on my server into the current web page. (both the css file and the javascript file will be hosted on my server).
Here's the "old school" way of doing it, which hopefully works across all browsers. In theory, you would use setAttribute unfortunately IE6 doesn't support it consistently.
var cssId = 'myCss'; // you could encode the css path itself to generate id..
if (!document.getElementById(cssId))
{
var head = document.getElementsByTagName('head')[0];
var link = document.createElement('link');
link.id = cssId;
link.rel = 'stylesheet';
link.type = 'text/css';
link.href = 'http://website.example/css/stylesheet.css';
link.media = 'all';
head.appendChild(link);
}
This example checks if the CSS was already added so it adds it only once.
Put that code into a JavaScript file, have the end-user simply include the JavaScript, and make sure the CSS path is absolute so it is loaded from your servers.
Here is an example that uses plain JavaScript to inject a CSS link into the head element based on the filename portion of the URL:
<script type="text/javascript">
var file = location.pathname.split( "/" ).pop();
var link = document.createElement( "link" );
link.href = file.substr( 0, file.lastIndexOf( "." ) ) + ".css";
link.type = "text/css";
link.rel = "stylesheet";
link.media = "screen,print";
document.getElementsByTagName( "head" )[0].appendChild( link );
</script>
Insert the code just before the closing head tag and the CSS will be loaded before the page is rendered. Using an external JavaScript (.js) file will cause a Flash of unstyled content (FOUC) to appear.
link.onload = function(){ ... } before appending –
Guildroy If you use jquery:
$('head').append('<link rel="stylesheet" type="text/css" href="style.css">');
$('head').append('<link rel="stylesheet" type="text/css" href="https://dl.dropboxusercontent.com/s/ep1nzckmvgjq7jr/remove_transitions_from_page.css">'); –
Agleam I guess something like this script would do:
<script type="text/javascript" src="/js/styles.js"></script>
This JS file contains the following statement:
if (!document.getElementById) document.write('<link rel="stylesheet" type="text/css" href="/css/versions4.css">');
The address of the javascript and css would need to be absolute if they are to refer to your site.
Many CSS import techniques are discussed in this "Say no to CSS hacks with branching techniques" article.
But the "Using JavaScript to dynamically add Portlet CSS stylesheets" article mentions also the CreateStyleSheet possibility (proprietary method for IE):
<script type="text/javascript">
//<![CDATA[
if(document.createStyleSheet) {
document.createStyleSheet('http://server/stylesheet.css');
}
else {
var styles = "@import url(' http://server/stylesheet.css ');";
var newSS=document.createElement('link');
newSS.rel='stylesheet';
newSS.href='data:text/css,'+escape(styles);
document.getElementsByTagName("head")[0].appendChild(newSS);
}
//]]>
document.createStyleSheet() to browsers which don't have it: #525196 –
Blissful document.write isn't recommended because it overwrites the entire body of your website. –
Gwynethgwynne <style> element instead of assuming it's the first child of <head> via ("head")[0]? –
Pusan var style = document.getElementsByTagName("style")[0]; –
Sielen Element.insertAdjacentHTML has very good browser support, and can add a stylesheet in one line.
document.head.insertAdjacentHTML(
'beforeend',
'<link rel="stylesheet" href="path/to/style.css" />');
If you want to know (or wait) until the style itself has loaded this works:
// this will work in IE 10, 11 and Safari/Chrome/Firefox/Edge
// add ES6 poly-fill for the Promise, if needed (or rewrite to use a callback)
let fetchStyle = function(url) {
return new Promise((resolve, reject) => {
let link = document.createElement('link');
link.type = 'text/css';
link.rel = 'stylesheet';
link.onload = () => resolve();
link.onerror = () => reject();
link.href = url;
let headScript = document.querySelector('script');
headScript.parentNode.insertBefore(link, headScript);
});
};
Usage:
fetchStyle(url)
.then(
() => console.log("style loaded succesfully"),
() => console.error("style could not be loaded"),
);
Use this code:
var element = document.createElement("link");
element.setAttribute("rel", "stylesheet");
element.setAttribute("type", "text/css");
element.setAttribute("href", "external.css");
document.getElementsByTagName("head")[0].appendChild(element);
In a modern browser you can use promise like this. Create a loader function with a promise in it:
function LoadCSS( cssURL ) {
// 'cssURL' is the stylesheet's URL, i.e. /css/styles.css
return new Promise( function( resolve, reject ) {
var link = document.createElement( 'link' );
link.rel = 'stylesheet';
link.href = cssURL;
document.head.appendChild( link );
link.onload = function() {
resolve();
console.log( 'CSS has loaded!' );
};
} );
}
Then obviously you want something done after the CSS has loaded. You can call the function that needs to run after CSS has loaded like this:
LoadCSS( 'css/styles.css' ).then( function() {
console.log( 'Another function is triggered after CSS had been loaded.' );
return DoAfterCSSHasLoaded();
} );
Useful links if you want to understand in-depth how it works:
I know this is a pretty old thread but here comes my 5 cents.
There is another way to do this depending on what your needs are.
I have a case where i want a css file to be active only a while. Like css switching. Activate the css and then after another event deativate it.
Instead of loading the css dynamically and then removing it you can add a Class/an id in front of all elements in the new css and then just switch that class/id of the base node of your css (like body tag).
You would with this solution have more css files initially loaded but you have a more dynamic way of switching css layouts.
Have you ever heard of Promises? They work on all modern browsers and are relatively simple to use. Have a look at this simple method to inject css to the html head:
function loadStyle(src) {
return new Promise(function (resolve, reject) {
let link = document.createElement('link');
link.href = src;
link.rel = 'stylesheet';
link.onload = () => resolve(link);
link.onerror = () => reject(new Error(`Style load error for ${src}`));
document.head.append(link);
});
}
You can implement it as follows:
window.onload = function () {
loadStyle("https://fonts.googleapis.com/css2?family=Raleway&display=swap")
.then(() => loadStyle("css/style.css"))
.then(() => loadStyle("css/icomoon.css"))
.then(() => {
alert('All styles are loaded!');
}).catch(console.error);
}
It's really cool, right? This is a way to decide the priority of the styles using Promises.
To see a multi-style loading implementation see: https://mcmap.net/q/56737/-inject-css-stylesheet-as-string-using-javascript
Here's a one line example, that uses plain JavaScript to inject a CSS link into the head element based on the filename portion of the URL:
document.head.innerHTML += '<link rel="stylesheet" href="css/style.css">';
Most browsers support it. See the browser compatibility.
id to the element and adding it only if it does not exist –
Tyrrell Answer from future. In 2022, we have import assertions api for import css file.
import mycss from "./style/mycss.css" assert { type: "css" };
document.adoptedStyleSheets = [sheet];
shadowRoot.adoptedStyleSheets = [sheet];
Browser support: till september 2022, only chromium based browsers and safari supported.
Read more at: v8 import assertions post
tc39 github t39 import assertions proposal
sheet and mycss variables / identifiers here? –
Evitaevitable Below a full code using for loading JS and/or CSS
function loadScript(directory, files){
var head = document.getElementsByTagName("head")[0]
var done = false
var extension = '.js'
for (var file of files){
var path = directory + file + extension
var script = document.createElement("script")
script.src = path
script.type = "text/javascript"
script.onload = script.onreadystatechange = function() {
if ( !done && (!this.readyState ||
this.readyState == "loaded" || this.readyState == "complete") ) {
done = true
script.onload = script.onreadystatechange = null // cleans up a little memory:
head.removeChild(script) // to avoid douple loading
}
};
head.appendChild(script)
done = false
}
}
function loadStyle(directory, files){
var head = document.getElementsByTagName("head")[0]
var extension = '.css'
for (var file of files){
var path = directory + file + extension
var link = document.createElement("link")
link.href = path
link.type = "text/css"
link.rel = "stylesheet"
head.appendChild(link)
}
}
(() => loadScript('libraries/', ['listen','functions', 'speak', 'commands', 'wsBrowser', 'main'])) ();
(() => loadScript('scripts/', ['index'])) ();
(() => loadStyle('styles/', ['index'])) ();
.onreadystatechange and this.readyState are not exists. When I try with script object, the only event work is .onload() from many events here ( developer.mozilla.org/en-US/docs/Web/API/GlobalEventHandlers ) nothing else seems to work. –
Milk This function uses memorization. And could be called many times with no conflicts of loading and running the same stylesheet twice. Also it's not resolving sooner than the stylesheet is actually loaded.
const loadStyle = function () {
let cache = {};
return function (src) {
return cache[src] || (cache[src] = new Promise((resolve, reject) => {
let s = document.createElement('link');
s.rel = 'stylesheet';
s.href = src;
s.onload = resolve;
s.onerror = reject;
document.head.append(s);
}));
}
}();
Please notice the parentheses () after the function expression.
Parallel loading of stylesheets:
Promise.all([
loadStyle('/style1.css'),
loadStyle('/style2.css'),
// ...
]).then(() => {
// do something
})
You can use the same method for dynamic loading scripts.
src is not used. The innner function is OK. But good example. –
Interfile There is a general jquery plugin that loads css and JS files synch and asych on demand. It also keeps track off what is already been loaded :) see: http://code.google.com/p/rloader/
Here's a way with jQuery's element creation method (my preference) and with callback onLoad:
var css = $("<link>", {
"rel" : "stylesheet",
"type" : "text/css",
"href" : "style.css"
})[0];
css.onload = function(){
console.log("CSS IN IFRAME LOADED");
};
document
.getElementsByTagName("head")[0]
.appendChild(css);
I'd like to share one more way to load not only css but all the assets (js, css, images) and handle onload event for the bunch of files. It's async-assets-loader. See the example below:
<script src="https://unpkg.com/async-assets-loader"></script>
<script>
var jsfile = "https://code.jquery.com/jquery-3.4.1.min.js";
var cssfile = "https://cdnjs.cloudflare.com/ajax/libs/materialize/1.0.0/css/materialize.min.css";
var imgfile = "https://logos.keycdn.com/keycdn-logo-black.png";
var assetsLoader = new asyncAssetsLoader();
assetsLoader.load([
{uri: jsfile, type: "script"},
{uri: cssfile, type: "style"},
{uri: imgfile, type: "img"}
], function () {
console.log("Assets are loaded");
console.log("Img width: " + assetsLoader.getLoadedTags()[imgfile].width);
});
</script>
According to the async-assets-loader docs
If you want no cache
var date = new Date().getTime();
document.head.innerHTML += '<link rel="stylesheet" type="text/css" href="/styles.css?='+date+'">';
The dynamic version using imports and assertion type css, when you want the style adopted just after an action.
(async ()=>{
const sheet = await import('./css/style.css', {assert: { type: 'css' }});
document.adoptedStyleSheets = [sheet]; // global
// or el.shadowRoot.adoptedStylesSheets = [sheet] for an element with shadow dom attached
})();
When needing to adopt more styles just push to it, since adoptedStyleSheets is an array :
document.addoptedStyles.push(style)
Or initlialize with multiple imports :
(async ()=>{
const sheet = await import('./css/style.css', {assert: { type: 'css' }});
const commonSheet = await import('./css/common-style.css', {assert: { type: 'css' }});
document.adoptedStyleSheets = [commonSheet, sheet]; // global
// or el.shadowRoot.adoptedStylesSheets = [commonSheet, sheet] for an element with shadow dom attached
})();
document.adoptedStyleSheets? If I need to import multiple stylesheets this way, won't they overwrite the existing ones instead of appending? –
Evitaevitable In 2024 with plain javascript I came out with this functions. If this may be any useful for someone else.
This functions can loads a CSS file/files and can be provided with a callback function nofifying you when the file/files is/are loaded and ready. This is tested and working code.
Edit: Also, this functions are safe to be called from a button click event for example, as it checks if a link to the css file already exist. If the css file is already loaded it will immediately call the onReady call back function.
/*
* Load a CSS file.
* @param {string} url : The url of the resourse to load.
* @param {function} onReady : Call back when the resource has been loaded.
*/
function getCss(url, onReady)
{
const links = document.querySelectorAll("link[href='" + url + "']");
if (links.length === 0)
{
var head = document.getElementsByTagName( "head" )[0];
var fileref = document.createElement("link");
fileref.setAttribute("rel", "stylesheet");
fileref.setAttribute("type", "text/css");
fileref.setAttribute("href", url);
if (onReady instanceof Function)
{
fileref.onload = onReady;
fileref.onreadystatechange = onReady;
}
head.insertBefore( fileref, head.firstChild );
}
else
{
if (onReady instanceof Function)
onReady();
}
}
/*
* Loads a list of css files.
* @param {array|string} urls : This can pass a single url, or an array of urls.
* @param {function} onReady : This is the callback after each css file has been loaded.
*/
function getCssList(urls, onReady)
{
if (Array.isArray(urls))
{
let awaiting = urls.length;
function doneAwaiting()
{
awaiting--;
if (awaiting === 0)
{
if (onReady instanceof Function)
onReady();
}
}
for (let i = 0; i < urls.length; i++)
{
getCss(urls[i], doneAwaiting);
}
}
else
{
getCss(urls, onReady);
}
}To use it simply
// Single css file.
getCss("url to css file", () => { /* do something when css is ready */ });
// a list of css files
getCssList
(
["url 1", "url 2", ...],
() =>
{
// Do something where css files are ready.
}
);var fileref = document.createElement("link")
fileref.setAttribute("rel", "stylesheet")
fileref.setAttribute("type", "text/css")
fileref.setAttribute("th:href", "@{/filepath}")
fileref.setAttribute("href", "/filepath")
I'm using thymeleaf and this is work fine. Thanks
th:href attribute on a client side? It won't be processed by Thymeleaf so it seems redundant here. –
Anhedral use:
document.getElementById("of head/body tag")
.innerHTML += '<link rel="stylesheet" type="text/css" href="style.css">';
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