How to load up CSS files using Javascript?
JavascriptHtmlCssDhtmlJavascript Problem Overview
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).
Javascript Solutions
Solution 1 - Javascript
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.com/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.
VanillaJS
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.
Solution 2 - Javascript
If you use jquery:
$('head').append('<link rel="stylesheet" type="text/css" href="style.css">');
Solution 3 - Javascript
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);
}
//]]>
Solution 4 - Javascript
Element.insertAdjacentHTML has very good browser support, and can add a stylesheet in one line.
document.getElementsByTagName("head")[0].insertAdjacentHTML(
"beforeend",
"<link rel=\"stylesheet\" href=\"path/to/style.css\" />");
Solution 5 - Javascript
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 = function() { resolve(); console.log('style has loaded'); };
link.href = url;
let headScript = document.querySelector('script');
headScript.parentNode.insertBefore(link, headScript);
});
};
Solution 6 - Javascript
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:
Solution 7 - Javascript
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);
Solution 8 - Javascript
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.
Solution 9 - Javascript
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(err => alert(err));
}
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://stackoverflow.com/a/63936671/13720928
Solution 10 - Javascript
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/
Solution 11 - Javascript
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);
Solution 12 - Javascript
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'])) ();
Solution 13 - 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.
Solution 14 - Javascript
You may use for this YUI library or use this article to implement
Solution 15 - Javascript
The YUI library might be what you are looking for. It also supports cross domain loading.
If you use jquery, this plugin does the same thing.
Solution 16 - Javascript
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
Solution 17 - Javascript
var elem = document.createElement('link');
elem.rel = ' stylesheet'
elem.href= 'style.css';//Link of the css file
document.head.appendChild(elem);
Solution 18 - Javascript
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
Solution 19 - Javascript
use:
document.getElementById("of head/body tag")
.innerHTML += '<link rel="stylesheet" type="text/css" href="style.css">';
Solution 20 - Javascript
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 (src) {
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.