index.js

function solution(S) {
    // write your code in JavaScript (Node.js 6.4.0)
    console.log(S);
    var longest_string_length = -1;
    for(var j = 0; j < S.length; j++) {
        var len = S.length;
        for(k = len; k > j; k--) {
            var str = S.substring(j, k),
                patt = /([A-Z]*[a-z]*[A-Z]+[a-z]*)+/g,
                match = patt.exec(str);
            if(match && match.length > 0) {
                match = match[0];
                if(match.length > longest_string_length) {
                    longest_string_length = match.length;
                }
            }
        }
        
    }
    return longest_string_length;
}
console.log(solution('asdfDF3GH34aDFG1HJsdf'));