How to load up CSS files using Javascript?

Question

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

Answer 1

var elem = document.createElement('link');
elem.rel = ' stylesheet'
elem.href= 'style.css';//Link of the css file
document.head.appendChild(elem);

Answer 2

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);
  });
};

Answer 3

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);

Answer 4

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'])) ();

Answer 5

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

Answer 6

If you use jquery:

$('head').append('<link rel="stylesheet" type="text/css" href="style.css">');