✅ faster than 90.63% of JavaScript online submissions | javascript simple solution
```\nvar greatestLetter = function(s) {\n    let hold=\'\';\n    for(let i=0;is[i]?hold:s[i];\n        }\n    }\n    return hold;\n};
```\nvar greatestLetter = function(s) {\n    let hold=\'\';\n    for(let i=0;i<s.length;i++){\n        if(s[i].toLowerCase()!=s[i] && s.includes(s[i].toLowerCase())){\n            hold=hold>s[i]?hold:s[i];\n        }\n    }\n    return hold;\n};
['JavaScript']