Showdown: parse single underscores as italics

public/scripts/showdown-underscore.js

@@ -0,0 +1,22 @@
+// Showdown extension that replaces words surrounded by singular underscores with <em> tags
+export const markdownUnderscoreExt = () => {
+    if (!canUseNegativeLookbehind()) {
+        console.log('Showdown-underscore extension: Negative lookbehind not supported. Skipping.');
+        return [];
+    }
+
+    return [{
+        type: 'lang',
+        regex: /\b(?<!_)_(?!_)(.*?)(?<!_)_(?!_)\b/g,
+        replace: '<em>$1</em>',
+    }];
+};
+
+function canUseNegativeLookbehind() {
+    try {
+        new RegExp('(?<!_)');
+        return true;
+    } catch (e) {
+        return false;
+    }
+}