Daily Challenge #100 - Round Up

likes :: [String] -> String
likes []        = "no one likes this"
likes [a]       = a ++ " likes this"
likes [a, b]    = a ++ " and " ++ b ++ " like this"
likes [a, b, c] = a ++ ", " ++ b ++ " and " ++ c ++ " like this"
likes (a:b:xs)  = a ++ ", " ++ b ++ " and " ++ (show $ length xs) ++ " others like this"

const convertIPStringToNumber = ipString => ipString.split(".")
    .reduce((acc, part) => (acc << 8) | Number(part), 0);

const ipsBetween = (start, finish) => 
    Math.abs(convertIPStringToNumber(finish) - convertIPStringToNumber(start));

package find

// MissingLetter indicates what the missing character is in a ordered sequence of characters
func MissingLetter(chars []rune) rune {
    var last int

    for _, r := range chars {
        if last != 0 && int(r)-last > 1 {
            return rune(r - 1)
        }
        last = int(r)
    }

    return rune(last)
}

package find

import "testing"

type testCase struct {
    description string
    input       []rune
    expected    rune
}

func TestMissingLetter(t *testing.T) {
    testCases := []testCase{
        {
            "two characters",
            []rune{'A', 'C'},
            'B',
        },
        {
            "dev-to example one",
            []rune{'a', 'b', 'c', 'd', 'f'},
            'e',
        },
        {
            "dev-to example two",
            []rune{'O', 'Q', 'R', 'S'},
            'P',
        },
    }

    for _, test := range testCases {
        if result := MissingLetter(test.input); result != test.expected {
            t.Fatalf("FAIL: %s - MissingLetter(%+v): %v - expected %v", test.description, test.input, result, test.expected)
        }
        t.Logf("PASS: %s", test.description)
    }
}

f=(s)=>[...Array(26)].map((_,i)=>26-i).map(n=>`key: ${26-n}\ncipher: ${s}\nplain: ${[...s].map(l=>(a=l.charCodeAt(0),String.fromCharCode(a<123&&a>96?97+((a-97+n)%26):a))).join('')}`).join`\n---\n`

f('dwwdfn iurp wkh zrrgv dw gdzq');

"key: 0
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: dwwdfn iurp wkh zrrgv dw gdzq
---
key: 1
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: cvvcem htqo vjg yqqfu cv fcyp
---
key: 2
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: buubdl gspn uif xppet bu ebxo
---
key: 3
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: attack from the woods at dawn
---
key: 4
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: zsszbj eqnl sgd vnncr zs czvm
---
key: 5
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: yrryai dpmk rfc ummbq yr byul
---
key: 6
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: xqqxzh colj qeb tllap xq axtk
---
key: 7
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: wppwyg bnki pda skkzo wp zwsj
---
key: 8
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: voovxf amjh ocz rjjyn vo yvri
---
key: 9
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: unnuwe zlig nby qiixm un xuqh
---
key: 10
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: tmmtvd ykhf max phhwl tm wtpg
---
key: 11
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: sllsuc xjge lzw oggvk sl vsof
---
key: 12
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: rkkrtb wifd kyv nffuj rk urne
---
key: 13
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: qjjqsa vhec jxu meeti qj tqmd
---
key: 14
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: piiprz ugdb iwt lddsh pi splc
---
key: 15
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: ohhoqy tfca hvs kccrg oh rokb
---
key: 16
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: nggnpx sebz gur jbbqf ng qnja
---
key: 17
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: mffmow rday ftq iaape mf pmiz
---
key: 18
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: leelnv qczx esp hzzod le olhy
---
key: 19
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: kddkmu pbyw dro gyync kd nkgx
---
key: 20
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: jccjlt oaxv cqn fxxmb jc mjfw
---
key: 21
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: ibbiks nzwu bpm ewwla ib liev
---
key: 22
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: haahjr myvt aol dvvkz ha khdu
---
key: 23
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: gzzgiq lxus znk cuujy gz jgct
---
key: 24
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: fyyfhp kwtr ymj bttix fy ifbs
---
key: 25
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: exxego jvsq xli asshw ex hear"