Surround selected text with typed char

in markdown fields.  Supports

- ` backtick
- ‘ single quotes
- “ double quotes
- _ underscore (wraps the text in the markdown italic character)
- * asterisk (wraps the text in the markdown bold characters, **)
- [ brackets
- < angle brackets
- ( parentheses

app/assets/javascripts/lib/utils/text_markdown.js

@@ -303,7 +303,40 @@ function updateText({ textArea, tag, cursorOffset, blockTag, wrap, select, tagCo
   });
 }
 
+/* eslint-disable @gitlab/require-i18n-strings */
+export function keypressNoteText(e) {
+  if (this.selectionStart === this.selectionEnd) {
+    return;
+  }
+  const keys = {
+    '*': '**{text}**', // wraps with bold character
+    _: '_{text}_', // wraps with italic character
+    '`': '`{text}`', // wraps with inline character
+    "'": "'{text}'", // single quotes
+    '"': '"{text}"', // double quotes
+    '[': '[{text}]', // brackets
+    '{': '{{text}}', // braces
+    '(': '({text})', // parentheses
+    '<': '<{text}>', // angle brackets
+  };
+  const tag = keys[e.key];
+
+  if (tag) {
+    updateText({
+      tag,
+      textArea: this,
+      blockTag: '',
+      wrap: true,
+      select: '',
+      tagContent: '',
+    });
+    e.preventDefault();
+  }
+}
+/* eslint-enable @gitlab/require-i18n-strings */
+
 export function addMarkdownListeners(form) {
+  $('.markdown-area').on('keydown', keypressNoteText);
   return $('.js-md', form)
     .off('click')
     .on('click', function() {
@@ -340,5 +373,6 @@ export function addEditorMarkdownListeners(editor) {
 }
 
 export function removeMarkdownListeners(form) {
+  $('.markdown-area').off('keydown');
   return $('.js-md', form).off('click');
 }

changelogs/unreleased/bw-surround-text-wth-char.yml

+---
+title: Surround selected text in markdown fields on certain key presses
+merge_request: 25748
+author:
+type: added

spec/frontend/lib/utils/text_markdown_spec.js

-import { insertMarkdownText } from '~/lib/utils/text_markdown';
+import { insertMarkdownText, keypressNoteText } from '~/lib/utils/text_markdown';
 
 describe('init markdown', () => {
   let textArea;
@@ -115,14 +115,15 @@ describe('init markdown', () => {
     describe('with selection', () => {
       const text = 'initial selected value';
       const selected = 'selected';
+      let selectedIndex;
+
       beforeEach(() => {
         textArea.value = text;
-        const selectedIndex = text.indexOf(selected);
+        selectedIndex = text.indexOf(selected);
         textArea.setSelectionRange(selectedIndex, selectedIndex + selected.length);
       });
 
       it('applies the tag to the selected value', () => {
-        const selectedIndex = text.indexOf(selected);
         const tag = '*';
 
         insertMarkdownText({
@@ -153,6 +154,29 @@ describe('init markdown', () => {
         expect(textArea.value).toEqual(text.replace(selected, `[${selected}](url)`));
       });
 
+      it.each`
+        key    | expected
+        ${'['} | ${`[${selected}]`}
+        ${'*'} | ${`**${selected}**`}
+        ${"'"} | ${`'${selected}'`}
+        ${'_'} | ${`_${selected}_`}
+        ${'`'} | ${`\`${selected}\``}
+        ${'"'} | ${`"${selected}"`}
+        ${'{'} | ${`{${selected}}`}
+        ${'('} | ${`(${selected})`}
+        ${'<'} | ${`<${selected}>`}
+      `('generates $expected when $key is pressed', ({ key, expected }) => {
+        const event = new KeyboardEvent('keydown', { key });
+
+        textArea.addEventListener('keydown', keypressNoteText);
+        textArea.dispatchEvent(event);
+
+        expect(textArea.value).toEqual(text.replace(selected, expected));
+
+        // cursor placement should be after selection + 2 tag lengths
+        expect(textArea.selectionStart).toBe(selectedIndex + expected.length);
+      });
+
       describe('and text to be selected', () => {
         const tag = '[{text}](url)';
         const select = 'url';
@@ -178,7 +202,7 @@ describe('init markdown', () => {
         it('selects the right text when multiple tags are present', () => {
           const initialValue = `${tag} ${tag} ${selected}`;
           textArea.value = initialValue;
-          const selectedIndex = initialValue.indexOf(selected);
+          selectedIndex = initialValue.indexOf(selected);
           textArea.setSelectionRange(selectedIndex, selectedIndex + selected.length);
           insertMarkdownText({
             textArea,
@@ -204,7 +228,7 @@ describe('init markdown', () => {
           const initialValue = `text ${expectedUrl} text`;
 
           textArea.value = initialValue;
-          const selectedIndex = initialValue.indexOf(expectedUrl);
+          selectedIndex = initialValue.indexOf(expectedUrl);
           textArea.setSelectionRange(selectedIndex, selectedIndex + expectedUrl.length);
 
           insertMarkdownText({