What is Caesar Cipher?
In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on. The method is named after Julius Caesar, who used it in his private correspondence.
Code
const caesarCipher = (str, shift) => { const letters = 'abcdefghijklmnopqrstuvwxyz'.split(''); let res = ''; for (let i = 0; i < str.length; i++) { const char = str[i]; const ind = letters.indexOf(char); if (ind === -1) { res += char; continue; } const encodedIndex = (ind + shift) % 26; res += letters[encodedIndex]; } return res; }; Mocha Test
mocha.setup('bdd'); const { assert } = chai; describe('caesarCipher()', () => { it('Shifting Letters Successfully', () => { assert.equal(caesarCipher('c', -2), 'a'); assert.equal(caesarCipher('abcd', 1), 'bcde'); assert.equal(caesarCipher('yz', 1), 'za'); assert.equal(caesarCipher('abcd', 100), 'wxyz'); }); it("Doesn't shift non-alphabetic Characters", () => { assert.equal(caesarCipher('gurer ner 9 qbtf!', 13), 'there are 9 dogs!'); }); }); mocha.run(); 
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