Consecutive-strings.js

/*
  You are given an array(list) strarr of strings and an integer k.
  Your task is to return the first longest string consisting of k consecutive strings taken in the array.

  Examples:
  strarr = ["tree", "foling", "trashy", "blue", "abcdef", "uvwxyz"], k = 2

  Concatenate the consecutive strings of strarr by 2, we get:

  treefoling   (length 10)  concatenation of strarr[0] and strarr[1]
  folingtrashy ("      12)  concatenation of strarr[1] and strarr[2]
  trashyblue   ("      10)  concatenation of strarr[2] and strarr[3]
  blueabcdef   ("      10)  concatenation of strarr[3] and strarr[4]
  abcdefuvwxyz ("      12)  concatenation of strarr[4] and strarr[5]

  Two strings are the longest: "folingtrashy" and "abcdefuvwxyz".
  The first that came is "folingtrashy" so 
  longest_consec(strarr, 2) should return "folingtrashy".

  In the same way:
  longest_consec(["zone", "abigail", "theta", "form", "libe", "zas", "theta", "abigail"], 2) --> "abigailtheta"
  n being the length of the string array, if n = 0 or k > n or k <= 0 return "" (return Nothing in Elm, "nothing" in Erlang).

  Note
  consecutive strings : follow one after another without an interruption
*/

// Answer:

function longestConsec(strarr, k) {
  if (strarr.length === 0 || k > strarr.length || k <= 0) return '';
  let result = '';
  strarr.forEach((element, index) => {
    let newStr = '';
    let counter = 0;
    for (let i = index; counter < k && i < strarr.length; counter++) {
      newStr = newStr + strarr[i];
      i++;
    }
    if (newStr.length > result.length) {
      result = newStr;
    }
  });
  return result;
}

// BigO: O(n)