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js/loadCSS.js

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+/*! loadCSS. [c]2017 Filament Group, Inc. MIT License */
+(function(w){
+    "use strict";
+    /* exported loadCSS */
+    var 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";
+
+        // wait until body is defined before injecting link. This ensures a non-blocking load in IE11.
+        function ready( cb ){
+            if( doc.body ){
+                return cb();
+            }
+            setTimeout(function(){
+                ready( cb );
+            });
+        }
+        // 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/
+        ready( function(){
+            ref.parentNode.insertBefore( ss, ( before ? ref : ref.nextSibling ) );
+        });
+        // A method (exposed on return object for external use) that mimics onload by polling 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 );
+            });
+        };
+
+        function loadCB(){
+            if( ss.addEventListener ){
+                ss.removeEventListener( "load", loadCB );
+            }
+            ss.media = media || "all";
+        }
+
+        // once loaded, set link's media back to `all` so that the stylesheet applies once it loads
+        if( ss.addEventListener ){
+            ss.addEventListener( "load", loadCB);
+        }
+        ss.onloadcssdefined = onloadcssdefined;
+        onloadcssdefined( loadCB );
+        return ss;
+    };
+    // commonjs
+    if( typeof exports !== "undefined" ){
+        exports.loadCSS = loadCSS;
+    }
+    else {
+        w.loadCSS = loadCSS;
+    }
+}( typeof global !== "undefined" ? global : this ));