task 6.js

const signal = `qzbzwwghwhwdhdqhhbhfbfsstggdsssgzgdzzdbbbzmbzzvlldppjnjlltwtsszwswgssjnsjnnfqfzqqjzjfjmfmwfmfhfnnmdnmnllbzzlbzlzflldzdbzbsbdddpgdppzhphhjjtccjgcgrgjgcjgjjsbjbffsgsqqrsqqgppgmgcmmrdrqdqbqmmctchcgcdgdwdwcdcjcfjccmpmlpllqqpmpllhfhchppwwdmdhdphpvprrhwhgwwlrwlwggwlwqqnmqnqrrbbzdzwddqzznllzwlljsscqqtlltppqspswsttlrttnvvvwllfslsjsfjssnqnbbbvgvlltjtltjljmljjfgfbggcbgbmbjjvwjvjgvgzvvzddrjdddrwrlrlgldlhlwwcddbsbbtwwcssrnndvvsbsnbsbmbnmngnpgpphfhzhshllltqtppnrrzpzrpzzrttmbmssbrbmbsmsnspnsncscwwmjwmwdmwmrmvmqvqvjqvvnrrtntwwwwsrwrnwnrwwwlslrlhrllvpvhppdpprrgzrgzggqmqgmgvghhsmhhjljfflrflfrlrzzbjjqmmmcncddvhhzjjqzzjfzzbssjqqtsqtqccmttdhttmwtmtffspplhlrhrdhhhpghgrhrchhmgmqgqlglssvnnwrrrrqqbmmpgmpmdmmljlflzzjttqntqqcnqccrvcczffclffmvfvwvmvnvsvnvffczzljzztdtztcztctbtppmrprqprpbbhlhphphhvppvdvmddvcctvvjbvvpmpbpnpllvclvlqlwqqpcpffdwdsdttzftfddbrrgsrgsgvgpgjpggfvgfvvtqtnnscssmnnfqnnblnnjlnlbbjrrmmpgmgnnqbbcjbcjbbmjjljsjrsjrsrwrgwgpgqgccqppfdpdssffgdgwddcvdvzzpttjlttmwwhnnlntncttfvfwvvwrvrwwlhlwlvwvzvpvfpvvsbslblrlssjddwhwfhwffqjfjzfjfmfrrvsrrlbrrdfdmdwmddpnpfnpfnfppczpprzprpvpjjtltptvvrgvvsttflfvfqqhnnbmnbmmpsptpdpttrbbhjbbdnntppbsbmssgccfdfflppbcpbblclrlhrhttffvqqvvnpnmpnnrbnnhqnqrrwvwrrbvbffcvctcjcwwmzmvvtdvtvbtblbvlbvlvdvdrdsrdrprllnzznzhhcjjsgglfglgrlrwwfcfzfjzfztfztzggffjftjffcbfbhhwfwnnbssrpsppmllszstztwwgbwgbgtbgggztgztzwtztbbrffznndhdmmqggssjfssrgssbnsndnqnvqvqvjqvqttlctltvlttrzrqrrdprddpqqvppvddgmdddpldllnvvjdjcjdjvvznzqqbgqbgbpbnbvvdjvvsnndsdjjjhnhggrnnrvrvlvqllqhhsbhssvvlhlssgqgmqqcscpsspsrpsrpspvvdmvdvwwcjwwvhwvvmzvzvfvccfzczjccscbcrcjrrrsgrsspnsntsnnrnwwhdwwzhzbbwgwcgglvlttqrttvrrgprrljlddnttqrqffgdfgdgzzhghthhmdmsmtsshhsfhhgzgvzgzwzffvlffzjjrttsdddbldljlvjvjttwdwzzrbblwbbgmbmgmbggbdbsbqqwzzgnzgzczpzfztftbtwbtbsttrwrfrssbrrdqdjqdqppdsswrwttmgmllqbqnnpspjjzjjmbbsddgjgbjggqqlgqgmgdmmwcmwcmwwsddvgvpphmhqmmlvlpvlpltllphhcshhrsrgsgzssspjspplgghvvwhwgwssbhshvvscshhbccbtcbcvvmnndsdwwbzbffhmmbppfjppbsblbtlltggzczdczdzjdjpjtppwdwlwqwnwjnnvttmcmzzqccvfcvvmrmzmwmhmttgdgmsrlddnbgqfbbmrpdglpbtdqpmctzjrffvvqnltcqlfddwqhvjpzhczzwhsmjtrpgsdtqlcqsljsjzqwhcfwttgghsjqhzqlgjzgrtgttwblpprbppcpzsbntrwwmvfvbmjjrjwjqcjhnstmvwzrbnjpzznnctrtllzhtwttntjqwjnfspzccqpjlzbncgbjjjztbgfmzflzsqflflcrfhtlsgbdfdbtwwqfdrqhzmmqdqthwzwqqqzddfvbwhnqwqtgwhtzlqqpwhcjhglcmmncvfcmqdwnzzmjbflwjrcjzwcblftzrpdcjzcmtzccjbsqmcnfmbsmrvlhswnmrqdczvvzzcnffgljdbtlvjgrqttcjhjmcdllnvhcdpztqghfgvjcqmqvmdwhcgrtwpjlmjfbqmnjnbvvjczcwfcrhcgzmsvmjlplcpghnqtpzddnwtmrwmqwbttsnlngszfbnslqvlbzbfzqnjpdvcdpmjpmmjhvzwwgzfjfqwbqwrznhsdpjgsvzlsrtlmhjrfnwrmljlqzwnfnsmqtzfsldwrgmbrrvcmmmdmwflwnvpwsrrstmffwbtwqmjzdnzbwmqfrfdgsmhzhprdsgsqtljqhtdqmvnzlwhrrqqftbvnhmjnzvmbdqpjhzjnszgcfptfcmthpfcvfvdmwdswzfgwjblglfbpfvvwrmnzlcvtgqbcrhfqlffrznnhbtbwdwdldthbhdsqvnghpqdlvpfmzhjbtdhfmrdzpghtppmvddnphcnnczvznwzrvtcwvpslhrhmhzbzqtjqjvdpwncjbqdnwwpnfblqtqdwwqncbvtsncfhgncrprvhvzppwjfpdmtdrmtfcqdmdhwzrhpnrvspfbzhsvlpwzgrrhnrllhmpcdfcqdhcnphlffpbfmbsznmvfdgshbsjcjjvhqqfpmjgpdpcrglbqdrnqmftqtnwcsgqzdwntfplsnlhdbdmcgwfldzzgmzjsdnldbnlnhjqhpmnsljsbhrglhjbbrmlhrmjnvzhnlvnfpdzfzwwdpzwhnqhlbqhrgfmvzpctdvscqbgznzdsvvvvcjnmbzlvsptslmqnggqjcmgvtgbnrzlmzqzmtdfvhjqqcpvbngmngjvrtcfvsmbvthvhmdcfhthmnjcvsvmsbwsjtmrwshspcsmnhvzqvglntngbmgtdngbvvcjrznpdmmsssljnnqjwwfzgwtlfqqpsqghjgrghldrcdmcqvqdjsfrfrnlnvltpfjhmcclwbsdcbmvmlnwltztfggzmrtnsczwvqgpqtwffmphprgrmjlnftlgqjvrngbcndlmrblmvcjsdhdcmtgsztjttpbgcznfcgdwfwdnqmrrjgdgrgshjfjqrbsjdhblvrqhlfphnbdslrjszcnpfhhwrfhhdvqbjpsmzznzbtbsgcggtctfbsrscvzlplfhlwjlrmzhbwjqhffdhrwcdctwvttwqzbdtrhdhdvtgvdbzjtqvdgbpwtzqqqnljztgpbjjcrgdgmrrsfvngcdbgzvcfpdppbgfrmmdnqdvtlwwglmghjwfjjrwjfnwgwdplbmlfljhsmshwvvvtdnvfcbbwplwnvzfcjwgsrrlctpsrhprttcjgcmfsjggfvbbljsbjtzplvjdwnwgsgvvntjwdwdqbwmtnnlgdcmfcccnwnrjlqtznjhdzwfpbzhjdmwwpcmffcwsnpfhmgqgwwnvpmqvrdfhlqtghrrbggdmtvpqgqsspmchnrqnrmqlddnspcdrwqpvclhrvjtzhpvthpltwqqbrdfjtnwncwrmdqszdpmmdzmjwjvqnfszvbchfdvwzhtrfgfhfmgwprdpqgmbfntsqztvqmtjvgbsjvzsbhfznbbzrstqbrrmqdjcztmfpnwbmvtccmvlhtvmgfdzcchbccrzznscbdwrdtnpslvcqmgrrvwhnjgjdpvbfgsdtdcmhpnwfwnnntqjqnwzfwnhsrjbhtqtlncvsnhgvtntfwldqfzztcdctsscfdmtnmdqgqgwmtqhlmswtqrvqbchdwtjsdlqjvfjdtmzlvrzwvfprzvjzrrfn`;

// part 1

const marker_finder = (stream, marker_size = 4) => {
  const marker = [];
  stream.split("").every((l) => {
    if (marker.length == marker_size) return false;

    if (marker.includes(l)) {
      marker.splice(0, marker.indexOf(l) + 1);
    }
    if (marker.length < marker_size) {
      marker.push(l);
    }

    return true;
  });
  return stream.indexOf(marker.join("")) + marker_size;
};

console.assert(
  marker_finder(`mjqjpqmgbljsphdztnvjfqwrcgsmlb`) == 7,
  "mjqjpqmgbljsphdztnvjfqwrcgsmlb: first marker after character 7"
);
console.assert(
  marker_finder(`bvwbjplbgvbhsrlpgdmjqwftvncz`) == 5,
  "bvwbjplbgvbhsrlpgdmjqwftvncz: first marker after character 5"
);
console.assert(
  marker_finder(`nppdvjthqldpwncqszvftbrmjlhg`) == 6,
  "nppdvjthqldpwncqszvftbrmjlhg: first marker after character 6"
);
console.assert(
  marker_finder(`nznrnfrfntjfmvfwmzdfjlvtqnbhcprsg`) == 10,
  "nznrnfrfntjfmvfwmzdfjlvtqnbhcprsg: first marker after character 10"
);
console.assert(
  marker_finder(`zcfzfwzzqfrljwzlrfnpqdbhtmscgvjw`) == 11,
  "zcfzfwzzqfrljwzlrfnpqdbhtmscgvjw: first marker after character 11"
);

// solution for 1st part
console.table({
  "result 1": marker_finder(signal),
});

// 2nd part

console.assert(
  marker_finder(`mjqjpqmgbljsphdztnvjfqwrcgsmlb`, 14) == 19,
  "mjqjpqmgbljsphdztnvjfqwrcgsmlb: first marker after character 19"
);
console.assert(
  marker_finder(`bvwbjplbgvbhsrlpgdmjqwftvncz`, 14) == 23,
  "bvwbjplbgvbhsrlpgdmjqwftvncz: first marker after character 23"
);
console.assert(
  marker_finder(`nppdvjthqldpwncqszvftbrmjlhg`, 14) == 23,
  "nppdvjthqldpwncqszvftbrmjlhg: first marker after character 23"
);
console.assert(
  marker_finder(`nznrnfrfntjfmvfwmzdfjlvtqnbhcprsg`, 14) == 29,
  "nznrnfrfntjfmvfwmzdfjlvtqnbhcprsg: first marker after character 29"
);
console.assert(
  marker_finder(`zcfzfwzzqfrljwzlrfnpqdbhtmscgvjw`, 14) == 26,
  "zcfzfwzzqfrljwzlrfnpqdbhtmscgvjw: first marker after character 26"
);

// solution for 2nd part
console.table({
  "result 2": marker_finder(signal, 14),
});