From 8295aa6a5a73520642cd0fb8adaa142d6928fa25 Mon Sep 17 00:00:00 2001
From: Lennart Vogelsang <lennart@vogelsang.berlin>
Date: Tue, 7 Jun 2022 19:55:27 +0200
Subject: [PATCH 1/2] Changed: ignore output of previewRender if it is null

---
 src/js/easymde.js  | 12 ++++++++++--
 types/easymde.d.ts |  2 +-
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/js/easymde.js b/src/js/easymde.js
index 8d44e1f..4ad8077 100644
--- a/src/js/easymde.js
+++ b/src/js/easymde.js
@@ -1124,7 +1124,11 @@ function togglePreview(editor) {
             toolbar_div.className += ' disabled-for-preview';
         }
     }
-    preview.innerHTML = editor.options.previewRender(editor.value(), preview);
+
+    var preview_result = editor.options.previewRender(editor.value(), preview);
+    if (preview_result !== null) {
+        preview.innerHTML = preview_result;
+    }
 
 }
 
@@ -2849,7 +2853,11 @@ EasyMDE.prototype.value = function (val) {
         if (this.isPreviewActive()) {
             var wrapper = cm.getWrapperElement();
             var preview = wrapper.lastChild;
-            preview.innerHTML = this.options.previewRender(val, preview);
+            var preview_result = this.options.previewRender(val, preview);
+            if (preview_result !== null) {
+                preview.innerHTML = preview_result;
+            }
+
         }
         return this;
     }
diff --git a/types/easymde.d.ts b/types/easymde.d.ts
index b153634..d751c2b 100644
--- a/types/easymde.d.ts
+++ b/types/easymde.d.ts
@@ -196,7 +196,7 @@ declare namespace EasyMDE {
         previewClass?: string | ReadonlyArray<string>;
         previewImagesInEditor?: boolean;
         imagesPreviewHandler?: (src: string) => string,
-        previewRender?: (markdownPlaintext: string, previewElement: HTMLElement) => string;
+        previewRender?: (markdownPlaintext: string, previewElement: HTMLElement) => string | null;
         promptURLs?: boolean;
         renderingConfig?: RenderingOptions;
         shortcuts?: Shortcuts;

From 67f75535adc7b8814f79910f5dcbd34f6171e789 Mon Sep 17 00:00:00 2001
From: Lennart Vogelsang <lennart@vogelsang.berlin>
Date: Tue, 7 Jun 2022 20:11:27 +0200
Subject: [PATCH 2/2] Updated documentation

---
 README.md | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/README.md b/README.md
index 208e940..b66e42f 100644
--- a/README.md
+++ b/README.md
@@ -266,6 +266,11 @@ const editor = new EasyMDE({
             preview.innerHTML = customMarkdownParser(plainText);
         }, 250);
 
+        // If you return null, the innerHTML of the preview will not 
+        // be overwritten. Useful if you control the preview node's content via
+        // vdom diffing.
+        // return null;
+
         return "Loading...";
     },
     promptURLs: true,