Convert examples/learning/helloworld64.html to await/async

examples/learning/helloworld64.html

@@ -40,9 +40,10 @@
   // Opening PDF by passing its binary data as a string. It is still preferable
   // to use Uint8Array, but string or array-like structure will work too.
   var loadingTask = pdfjsLib.getDocument({ data: pdfData, });
-  loadingTask.promise.then(function(pdf) {
+  (async function() {
+    var pdf = await loadingTask.promise;
     // Fetch the first page.
-    pdf.getPage(1).then(function(page) {
+    var page = await pdf.getPage(1);
     var scale = 1.5;
     var viewport = page.getViewport({ scale: scale, });
     // Support HiDPI-screens.
@@ -64,12 +65,11 @@
     // Render PDF page into canvas context.
     var renderContext = {
       canvasContext: context,
-        transform: transform,
-        viewport: viewport,
+      transform,
+      viewport,
     };
     page.render(renderContext);
-    });
-  });
+  })();
 </script>
 
 <hr>