add isReady method to check reveal.js loaded state

js/reveal.js

@@ -96,6 +96,9 @@ var Reveal = (function(){
 			dependencies: []
 		},
 
+		// Flags if reveal.js is loaded (has dispatched the 'ready' event)
+		loaded = false,
+
 		// The current auto-slide duration
 		autoSlide = 0,
 
@@ -447,6 +450,8 @@ var Reveal = (function(){
 			// Enable transitions now that we're loaded
 			dom.slides.classList.remove( 'no-transition' );
 
+			loaded = true;
+
 			dispatchEvent( 'ready', {
 				'indexh': indexh,
 				'indexv': indexv,
@@ -2670,6 +2675,11 @@ var Reveal = (function(){
 			}
 		},
 
+		// Checks if reveal.js has been loaded and is ready for use
+		isReady: function() {
+			return loaded;
+		},
+
 		// Forward event binding to the reveal DOM element
 		addEventListener: function( type, listener, useCapture ) {
 			if( 'addEventListener' in window ) {