Frequency Sort
var frequencySort = function(s) {
    var obj = {};
    for(var i = 0; i < s.length; i++){
        if(!obj.hasOwnProperty(s[i])){
            obj[s[i]] = 1
        } else {
            obj[s[i]]++
        }
    }

    var returnStr = ''
    var count = 1;
    while(returnStr.length < s.length){
        for(var prop in obj){
            if(obj[prop] === count){
                for(var i = 0; i < obj[prop]; i++){

                }
            }

        }
        count++
    }
    return returnStr;
};


Is Subsequence
var isSubsequence = function(s, t) {

    for(var i = 0; i < t.length; i++){
         if(t[i] === s[0]){
            s = s.substring(1)
            isSubsequence(s.substring(1), t)
        }
    }
    return s === '';
};