vigenereCipher.js

// JavaScript code to implement Vigenere Cipher
 
// This function generates the key in
// a cyclic manner until it's length isn't
// equal to the length of original text
function generateKey(str,key)
{
     
     key=key.split("");
    if(str.length == key.length)
        return key.join("");
    else
    {
        let temp=key.length;    
        for (let i = 0;i<(str.length-temp) ; i++)
        {
             
            key.push(key[i % ((key).length)])
        }
    }
    return key.join("");
}
 
// This function returns the encrypted text
// generated with the help of the key
function cipherText(str,key)
{
    let cipher_text="";
  
    for (let i = 0; i < str.length; i++)
    {
        // converting in range 0-25
        let x = (str[i].charCodeAt(0) + key[i].charCodeAt(0)) %26;
  
        // convert into alphabets(ASCII)
        x += 'A'.charCodeAt(0);
  
        cipher_text+=String.fromCharCode(x);
    }
    return cipher_text;
}
 
// This function decrypts the encrypted text
// and returns the original text
function originalText(cipher_text,key)
{
    let orig_text="";
  
    for (let i = 0 ; i < cipher_text.length ; i++)
    {
        // converting in range 0-25
        let x = (cipher_text[i].charCodeAt(0) -
                    key[i].charCodeAt(0) + 26) %26;
  
        // convert into alphabets(ASCII)
        x += 'A'.charCodeAt(0);
        orig_text+=String.fromCharCode(x);
    }
    return orig_text;
}
 
// This function will convert the lower
// case character to Upper case
function LowerToUpper(s)
{
    let str =(s).split("");
    for(let i = 0; i < s.length; i++)
    {
        if(s[i] == s[i].toLowerCase())
        {
            str[i] = s[i].toUpperCase();
        }
    }
    s = str.toString();
    return s;
}
 
// Driver code
let str = "SIMFITKXLLVOB";
let keyword = "DEVDEGREE";
 
 
let key = generateKey(str, keyword);
 
let cipher_text = cipherText(str, key);
 
console.log("Ciphertext : "
                   + cipher_text);
 
console.log("Original/Decrypted Text : "
                   + originalText(cipher_text, key));
 
 
 
 
// This code is contributed by rag2127