.

.

/../.test(""); // true UTF-16 
/../u.test(""); // false Unicode 

function parseTitle(entry) {
  // 
  //  m  . 
  // 
  return /^#[ \t]+(.+)$/m.exec(entry)?.[1];
}

parseTitle("# "); // ""
parseTitle("## "); // undefined
parseTitle(`
---
slug: Web/JavaScript/Reference/Regular_expressions/Wildcard
---

# .

****
`); // " ."

function parseCodeBlock(entry) {
  return /^```.*?^(.+?)\n```/ms.exec(entry)?.[1];
}

parseCodeBlock(`
\`\`\`js
console.log("");
\`\`\`
`); // "console.log("");"

parseCodeBlock(`
\`try...catch\` 

\`\`\`js example-bad
try
  doSomething();
catch (e)
  console.log(e);
\`\`\`
`); // "try\n  doSomething();\ncatch (e)\n  console.log(e);"