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[yaffs-website] / web / modules / contrib / advagg / advagg_mod / js / loadCSS.js

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+/**
+ * @file
+ * Used to load CSS via JS so css doesn't block the browser.
+ */
+
+/* @codingStandardsIgnoreFile */
+
+/*!
+loadCSS: load a CSS file asynchronously.
+[c]2015 @scottjehl, Filament Group, Inc.
+Licensed MIT
+*/
+(function(w){
+  "use strict";
+  /* exported loadCSS */
+  w.loadCSS = function( href, before, media ){
+    // Arguments explained:
+    // `href` [REQUIRED] is the URL for your CSS file.
+    // `before` [OPTIONAL] is the element the script should use as a reference for injecting our stylesheet <link> before
+      // By default, loadCSS attempts to inject the link after the last stylesheet or script in the DOM. However, you might desire a more specific location in your document.
+    // `media` [OPTIONAL] is the media type or query of the stylesheet. By default it will be 'all'
+    var doc = w.document;
+    var ss = doc.createElement( "link" );
+    var ref;
+    if( before ){
+      ref = before;
+    }
+    else {
+      var refs = ( doc.body || doc.getElementsByTagName( "head" )[ 0 ] ).childNodes;
+      ref = refs[ refs.length - 1];
+    }
+
+    var sheets = doc.styleSheets;
+    ss.rel = "stylesheet";
+    ss.href = href;
+    // temporarily set media to something inapplicable to ensure it'll fetch without blocking render
+    ss.media = "only x";
+
+    // Inject link
+      // Note: the ternary preserves the existing behavior of "before" argument, but we could choose to change the argument to "after" in a later release and standardize on ref.nextSibling for all refs
+      // Note: `insertBefore` is used instead of `appendChild`, for safety re: http://www.paulirish.com/2011/surefire-dom-element-insertion/
+    ref.parentNode.insertBefore( ss, ( before ? ref : ref.nextSibling ) );
+    // A method (exposed on return object for external use) that mimics onload by polling until document.styleSheets until it includes the new sheet.
+    var onloadcssdefined = function( cb ){
+      var resolvedHref = ss.href;
+      var i = sheets.length;
+      while( i-- ){
+        if( sheets[ i ].href === resolvedHref ){
+          return cb();
+        }
+      }
+      setTimeout(function() {
+        onloadcssdefined( cb );
+      });
+    };
+
+    // once loaded, set link's media back to `all` so that the stylesheet applies once it loads
+    ss.onloadcssdefined = onloadcssdefined;
+    onloadcssdefined(function() {
+      ss.media = media || "all";
+    });
+    return ss;
+  };
+}(this));