fix microsoft#146750.

Author: rebornix

extensions/markdown-language-features/notebook/index.ts

@@ -204,7 +204,8 @@ export const activate: ActivationFunction<void> = (ctx) => {
 				previewNode.classList.add('emptyMarkdownCell');
 			} else {
 				previewNode.classList.remove('emptyMarkdownCell');
-				const markdownText = outputInfo.mime.startsWith('text/x-') ? `\`\`\`${outputInfo.mime.substr(7)}\n${text}\n\`\`\`` : text;
+				const markdownText = outputInfo.mime.startsWith('text/x-') ? `\`\`\`${outputInfo.mime.substr(7)}\n${text}\n\`\`\``
+					: (outputInfo.mime.startsWith('application/') ? `\`\`\`${outputInfo.mime.substr(12)}\n${text}\n\`\`\`` : text);
 				const unsanitizedRenderedMarkdown = markdownIt.render(markdownText);
 				previewNode.innerHTML = (ctx.workspace.isTrusted
 					? unsanitizedRenderedMarkdown

extensions/markdown-language-features/package.json

@@ -122,7 +122,8 @@
           "text/x-typescript",
           "text/x-vb",
           "text/x-xml",
-          "text/x-yaml"
+          "text/x-yaml",
+		  "application/json"
         ]
       }
     ],