U.Ahmad U.Ahmad - 6 months ago 56
Javascript Question

Dynamically loading css file using javascript with callback without jQuery

I am trying to load a css file dynamically using javascript and cannot use any other js library (eg jQuery).

The css file loads but I can't seem to get a callback to work for it. Below is the code I am using

var callbackFunc = function(){
console.log('file loaded');
};
var head = document.getElementsByTagName( "head" )[0];
var fileref=document.createElement("link");
fileref.setAttribute("rel", "stylesheet");
fileref.setAttribute("type", "text/css");
fileref.setAttribute("href", url);

fileref.onload = callbackFunc;
head.insertBefore( fileref, head.firstChild );


Using the following code to add a script tag to load a js file works and fires a callback:

var callbackFunc = function(){
console.log('file loaded');
};

var script = document.createElement("script");

script.setAttribute("src",url);
script.setAttribute("type","text/javascript");

script.onload = callbackFunc ;

head.insertBefore( script, head.firstChild );


Am I doing something wrong here? Any other method that can help me achieve this would be much appreciated?

Answer

Unfortunately there is no onload support for stylesheets in most modern browsers. There is a solution I found with a little Googling.

Cited from: http://thudjs.tumblr.com/post/637855087/stylesheet-onload-or-lack-thereof

The basics

The most basic implementation of this can be done in a measely 30 lines of — framework independent — JavaScript code:

function loadStyleSheet( path, fn, scope ) {
   var head = document.getElementsByTagName( 'head' )[0], // reference to document.head for appending/ removing link nodes
       link = document.createElement( 'link' );           // create the link node
   link.setAttribute( 'href', path );
   link.setAttribute( 'rel', 'stylesheet' );
   link.setAttribute( 'type', 'text/css' );

   var sheet, cssRules;
// get the correct properties to check for depending on the browser
   if ( 'sheet' in link ) {
      sheet = 'sheet'; cssRules = 'cssRules';
   }
   else {
      sheet = 'styleSheet'; cssRules = 'rules';
   }

   var interval_id = setInterval( function() {                     // start checking whether the style sheet has successfully loaded
          try {
             if ( link[sheet] && link[sheet][cssRules].length ) { // SUCCESS! our style sheet has loaded
                clearInterval( interval_id );                      // clear the counters
                clearTimeout( timeout_id );
                fn.call( scope || window, true, link );           // fire the callback with success == true
             }
          } catch( e ) {} finally {}
       }, 10 ),                                                   // how often to check if the stylesheet is loaded
       timeout_id = setTimeout( function() {       // start counting down till fail
          clearInterval( interval_id );             // clear the counters
          clearTimeout( timeout_id );
          head.removeChild( link );                // since the style sheet didn't load, remove the link node from the DOM
          fn.call( scope || window, false, link ); // fire the callback with success == false
       }, 15000 );                                 // how long to wait before failing

   head.appendChild( link );  // insert the link node into the DOM and start loading the style sheet

   return link; // return the link node;
}

This would allow you to load a style sheet with an onload callback function like this:

loadStyleSheet( '/path/to/my/stylesheet.css', function( success, link ) {
   if ( success ) {
      // code to execute if the style sheet was loaded successfully
   }
   else {
      // code to execute if the style sheet failed to successfully
   }
} );

Or if you want to your callback to maintain its scope/ context, you could do something kind of like this:

loadStyleSheet( '/path/to/my/stylesheet.css', this.onComplete, this );
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