Merge pull request #14138 from catherinemds/await/async-issue

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

examples/learning/helloworld.html

@@ -17,7 +17,7 @@
   // If absolute URL from the remote server is provided, configure the CORS
   // header on that server.
   //
-  var url = './helloworld.pdf';
+  const url = './helloworld.pdf';
 
   //
   // The workerSrc property shall be specified.
@@ -28,43 +28,43 @@
   //
   // Asynchronous download PDF
   //
-  var loadingTask = pdfjsLib.getDocument(url);
+  const loadingTask = pdfjsLib.getDocument(url);
-  loadingTask.promise.then(function(pdf) {
+  (async () => {
+    const pdf = await loadingTask.promise;
     //
     // Fetch the first page
     //
-    pdf.getPage(1).then(function(page) {
+    const page = await pdf.getPage(1);
-      var scale = 1.5;
+    const scale = 1.5;
-      var viewport = page.getViewport({ scale: scale, });
+    const viewport = page.getViewport({ scale });
-      // Support HiDPI-screens.
+    // Support HiDPI-screens.
-      var outputScale = window.devicePixelRatio || 1;
+    const outputScale = window.devicePixelRatio || 1;
 
-      //
+    //
-      // Prepare canvas using PDF page dimensions
+    // Prepare canvas using PDF page dimensions
-      //
+    //
-      var canvas = document.getElementById('the-canvas');
+    const canvas = document.getElementById("the-canvas");
-      var context = canvas.getContext('2d');
+    const context = canvas.getContext("2d");
 
-      canvas.width = Math.floor(viewport.width * outputScale);
+    canvas.width = Math.floor(viewport.width * outputScale);
-      canvas.height = Math.floor(viewport.height * outputScale);
+    canvas.height = Math.floor(viewport.height * outputScale);
-      canvas.style.width = Math.floor(viewport.width) + "px";
+    canvas.style.width = Math.floor(viewport.width) + "px";
-      canvas.style.height =  Math.floor(viewport.height) + "px";
+    canvas.style.height = Math.floor(viewport.height) + "px";
 
-      var transform = outputScale !== 1
+    const transform = outputScale !== 1 
-        ? [outputScale, 0, 0, outputScale, 0, 0]
+      ? [outputScale, 0, 0, outputScale, 0, 0] 
-        : null;
+      : null;
 
-      //
+    //
-      // Render PDF page into canvas context
+    // Render PDF page into canvas context
-      //
+    //
-      var renderContext = {
+    const renderContext = {
-        canvasContext: context,
+      canvasContext: context,
-        transform: transform,
+      transform,
-        viewport: viewport,
+      viewport,
-      };
+    };
-      page.render(renderContext);
+    page.render(renderContext);
-    });
+  })();
-  });
 </script>
 
 <hr>