inverse_fb.js

function inversefb(data) {    
    var _base = "1211213", base = "";
    var _value = [3,5,6,9,10,12,15], value = [];
    
    data = data.map(function(v){ return v == "Fizz" ? "1" : v == "Buzz" ? "2" : "3"}).join("");
    
    while(data.length > base.length) {
        base += _base;
        value = value.concat(_value);
    }
    for(var i=0; i<2; i++) {
        base += base;
        value = value.concat(value);
    }
    
    var pos = base.indexOf(data);
    if(pos == -1) {
        return "";
    }
    
    if(data.length == 1) {
        return value[pos].toString();
    }
    
    var tmpAns = [], lastAns = [];
    var stopper = 0;
    while(pos + data.length - 1 < value.length) {
        if(stopper > 5) break;
        var n = [ value[pos], value[pos + data.length - 1] ];
        if(n[0] > n[1]) {
            n[1] += Math.round(data.length / _base.length) * 15;
        }
        if(tmpAns.length == 0 || (tmpAns[1] - tmpAns[0] > n[1] - n[0])) {
            tmpAns = n;
            stopper = 0;
        } else {
            stopper++;
        }
        pos = base.indexOf(data, pos + 1);
    }
    return tmpAns.toString().replace(",", "..");
}

console.log([
    inversefb(["Fizz", "Buzz", "Fizz", "Fizz", "Buzz", "Fizz", "FizzBuzz"]),
    inversefb(["FizzBuzz", "Fizz", "Buzz", "Fizz"]),
    inversefb(["FizzBuzz", "Fizz", "Buzz", "Fizz", "Fizz", "Buzz"]),
    inversefb(["Buzz","Buzz"]), // Error
])