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

function longestConsec(strarr, k) {
    let arrayRes = [], longest = "";

    if (k <= 0) { return "" }
    for(let i = 0; k <= strarr.length; i++) {
        arrayRes.push(strarr.slice(i, k).join('')); // push into arrayRes the result of joining the elements from strarr[i] to strarr[k]
        k++;
    }
    for(el of arrayRes) {
        if (el.length > longest.length) {longest = el}; // going over the arrayRes looking for the longest string
    }
    return longest; // return the longest string
}