CODE EXAMPLE FOR JAVASCRIPT

javascript caesar cipher

const alphabet = [
	'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'
]
const MAX_ROT = alphabet.length

/**
 * Encrypt text  using spanish Cesar encryption
 * @memberof crypt/cesar
 * @param {string} text - A string to be encrypted
 * @param {number} rot - Scroll numer, can be from 0 to 26
 * @returns {string} - Encrypted text
 */
const encrypt = (text, rot = 3) => {
	if (rot > MAX_ROT || rot < 0) {
		throw Error('rot can be only beetween 0 to 26')
	}

	text = Array.from(text)

	const encryptedText = text.map((char) => {
		const isLower = char.toLowerCase()
		const idx = alphabet.indexOf(char.toUpperCase())

		if (idx === -1) {
			return char
		}

		const encryptedIdx = (idx + rot) % MAX_ROT
		const encryptedChar = alphabet[encryptedIdx]

		return isLower ? encryptedChar.toLowerCase() : encryptedChar
	})

	return encryptedText.join('')
}

/**
 * Decrypt text using spanish Cesar encryption
 * @memberof crypt/cesar
 * @param {string} text - A string to be decrypted
 * @param {number} rot - Scroll numer, can be from 0 to 26
 * @returns {string} - Decrypted text
 */
const decrypt = (text, rot = 3) => {
	if (rot > MAX_ROT || rot < 0) {
		throw Error('rot can be only beetween 0 to 26')
	}

	text = Array.from(text)

	const decryptedText = text.map((char) => {
		const isLower = char.toLowerCase()
		const idx = alphabet.indexOf(char.toUpperCase())

		if (idx === -1) {
			return char
		}

		let decryptedIdx = (idx - rot) % MAX_ROT

		decryptedIdx = decryptedIdx < 0 ? decryptedIdx + MAX_ROT : decryptedIdx

		const decryptedChar = alphabet[decryptedIdx]

		return isLower ? decryptedChar.toLowerCase() : decryptedChar
	})

	return decryptedText.join('')
}

console.log(encrypt('abcxyz', 5))
console.log(decrypt('fghcde', 5))