Added a Vigenere Cipher

VigenereCipher/index.js

@@ -0,0 +1,51 @@
+let letters = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"];
+
+let table = [letters]
+
+let plaintext = "ATTACKATDAWN";
+let key = "LEMON";
+let repeatKey = "";
+let solution = "";
+
+let remainder = plaintext.length % key.length;
+let round = Math.round(plaintext.length / key.length);
+
+for(let i = 0; i < round; i++){
+  repeatKey += key;
+}
+
+for(let i = 0; i < remainder; i++){
+  repeatKey += key[i];
+}
+
+
+//Set up tables
+function getLetterSet(set, index){
+  let first = set[0];
+  let newSet = [];
+  for(let i = 1; i <= 25; i++){
+    newSet.push(set[i])
+  }
+  newSet.push(first);
+  table.push(newSet);
+  if(index <= 23){
+    getLetterSet(newSet, index + 1);
+  }else{
+    return table;
+  }
+}
+
+let newTable = getLetterSet(letters, 0);
+
+
+//Solution
+for(let i = 0; i < plaintext.length; i++){
+  let plainLetter = plaintext[i];
+  let keyLetter = repeatKey[i];
+  let rowNum = letters.indexOf(keyLetter);
+  let colNum = letters.indexOf(plainLetter);
+  let cipher = table[rowNum][colNum];
+  solution += cipher;
+}
+
+console.log(solution)