[Javascript] Simple easy solution
\nvar greatestLetter = function (s) {\n  s = s.split("").sort().reverse()\n  for (let i = 0; i < s.length; i++) {\n    if (s[i] === s[i].toUpperCase() || s.leng
```\nvar greatestLetter = function (s) {\n  s = s.split("").sort().reverse()\n  for (let i = 0; i < s.length; i++) {\n    if (s[i] === s[i].toUpperCase() || s.length === 1) return \'\'\n    else {\n      if (s.includes(s[i].toUpperCase())) return s[i].toUpperCase()\n    }\n  }\n};\n```
['JavaScript']