Merge pull request michael-misshore#9 from michael-misshore/v1.2.1-update

Add cssrelpreload.js

Author: michael-misshore

README.md

@@ -18,6 +18,7 @@ The loadCSS and onloadCSS files will be added to the asset pipeline and availabl
 
 ```js
 //= require loadCSS
+//= require cssrelpreload
 //= require onloadCSS
 ```
 

lib/loadcss/rails/version.rb

@@ -1,6 +1,6 @@
 module LoadCSS
   module Rails
-    VERSION = '1.2.0'
-    LOADCSS_VERSION = '1.2.0'
+    VERSION = '1.2.1'
+    LOADCSS_VERSION = '1.2.1'
   end
 end

vendor/assets/javascripts/cssrelpreload.js

@@ -0,0 +1,43 @@
+/*! CSS rel=preload polyfill. Depends on loadCSS function. [c]2016 @scottjehl, Filament Group, Inc. Licensed MIT  */
+(function( w ){
+  // rel=preload support test
+  if( !w.loadCSS ){
+    return;
+  }
+  var rp = loadCSS.relpreload = {};
+  rp.support = function(){
+    try {
+      return w.document.createElement( "link" ).relList.supports( "preload" );
+    } catch (e) {
+      return false;
+    }
+  };
+
+  // loop preload links and fetch using loadCSS
+  rp.poly = function(){
+    var links = w.document.getElementsByTagName( "link" );
+    for( var i = 0; i < links.length; i++ ){
+      var link = links[ i ];
+      if( link.rel === "preload" && link.getAttribute( "as" ) === "style" ){
+        w.loadCSS( link.href, link );
+        link.rel = null;
+      }
+    }
+  };
+
+  // if link[rel=preload] is not supported, we must fetch the CSS manually using loadCSS
+  if( !rp.support() ){
+    rp.poly();
+    var run = w.setInterval( rp.poly, 300 );
+    if( w.addEventListener ){
+      w.addEventListener( "load", function(){
+        w.clearInterval( run );
+      } );
+    }
+    if( w.attachEvent ){
+      w.attachEvent( "onload", function(){
+        w.clearInterval( run );
+      } )
+    }
+  }
+}( this ));