Added web workers to improve performance.

Author: Clevis22

README.md

@@ -59,8 +59,6 @@ Enter your markdown on the left and see the live preview of the rendered output
 
 * Improve mobile styling
 
-* Improve performance for long documents
-
 * Add more export options
 
 * Fix exported PDF tables

index.html

@@ -22,7 +22,6 @@
     <meta name="twitter:image" content="screenshot.png">
     <link rel="stylesheet" href="dependencies/github-markdown.css">
     <link rel="stylesheet" href="style.css">
-
     <link rel="stylesheet" href="dependencies/highlight-default.css">
     <link rel="stylesheet" href="dependencies/atelier-cave.css">
   </head>

previewWorker.js

@@ -0,0 +1,16 @@
+importScripts('dependencies/showdown.js');
+
+self.addEventListener('message', function(event) {
+  // Instantiate a converter
+  var converter = new showdown.Converter({
+    tables: true,
+    strikethrough: true,
+    emoji: true
+  });
+
+  // Convert Markdown to HTML
+  var html = converter.makeHtml(event.data);
+
+  // Post the resulting HTML back to the main thread
+  self.postMessage(html);
+});

script.js

@@ -6,18 +6,18 @@ var converter = new showdown.Converter({
 var editor = document.getElementById('editor');
 var preview = document.getElementById('preview');
 
+var previewWorker = new Worker('previewWorker.js');
 function updatePreview() {
+  previewWorker.postMessage(editor.value);
+}
+previewWorker.addEventListener('message', function(event) {
   var scrollTop = preview.scrollTop;
-  preview.innerHTML = converter.makeHtml(editor.value);
+  preview.innerHTML = event.data;
   preview.scrollTop = scrollTop;
-
-  var markdownText = editor.value;
-  var html = converter.makeHtml(markdownText);
-  preview.innerHTML = html;
   preview.querySelectorAll('pre code').forEach((block) => {
     hljs.highlightBlock(block);
   });
-}
+});
 
 // Debounce function to limit the frequency of autosave invocations
 function debounce(func, wait) {